Electrochromic rearview mirror incorporating a third surface reflector

ABSTRACT

The inventive electrochromic mirror may be used in a vehicle rearview mirror assembly having a light source positioned behind the electrochromic mirror for selectively projecting light through the mirror and/or a light sensor positioned behind the electrochromic mirror for selectively receiving light through the mirror. The electrochromic mirror includes front and rear spaced elements each having front and rear surfaces and being sealably bonded together in a spaced-apart relationship to define a chamber, a layer of transparent conductive material disposed on the rear surface of the front element, an electrochromic material is contained within the chamber, and a second electrode overlies the front surface of the rear element in contact with the electrochromic material. The second electrode includes a layer of reflective material and a partially transmissive coating of and is disposed over substantially all of the front surface of the rear element. The second electrode further includes a region in front of the light source and/or light sensor that is at least partially transmissive.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/789,221, filed on Apr. 24, 2007, which is a continuation of U.S.patent application Ser. No. 11/348,363, filed on Feb. 6, 2006, now U.S.Pat. No. 7,209,277, which is a continuation of U.S. patent applicationSer. No. 10/893,594, filed on Jul. 16, 2004, now U.S. Pat. No.7,009,751, which is a continuation of U.S. patent application Ser. No.10/352,778, filed on Jan. 28, 2003, now U.S. Pat. No. 6,870,656, whichis a continuation of U.S. patent application Ser. No. 09/994,218, filedon Nov. 26, 2001, now U.S. Pat. No. 6,512,624, which is a continuationof U.S. patent application Ser. No. 09/311,955, filed on May 14, 1999,now U.S. Pat. No. 6,356,376. The entire disclosure of each of the aboveapplications is incorporated herein by reference.

BACKGROUND OF THE INVENTION

This invention relates to electrochromic rearview mirrors for motorvehicles and, more particularly, to improved electrochromic rearviewmirrors incorporating a third surface reflector/electrode in contactwith at least one solution-phase electrochromic material.

Heretofore, various rearview mirrors for motor vehicles have beenproposed which change from the full reflectance mode (day) to thepartial reflectance mode(s) (night) for glare-protection purposes fromlight emanating from the headlights of vehicles approaching from therear. Among such devices are those wherein the transmittance is variedby thermochromic, photochromic, or electro-optic means (e.g., liquidcrystal, dipolar suspension, electrophoretic, electrochromic, etc.) andwhere the variable transmittance characteristic affects electromagneticradiation that is at least partly in the visible spectrum (wavelengthsfrom about 3800 Å to about 7800 Å). Devices of reversibly variabletransmittance to electromagnetic radiation have been proposed as thevariable transmittance element in variable transmittance light-filters,variable reflectance mirrors, and display devices, which employ suchlight-filters or mirrors in conveying information. These variabletransmittance light filters have included windows.

Devices of reversibly variable transmittance to electromagneticradiation, wherein the transmittance is altered by electrochromic means,are described, for example, by Chang, “Electrochromic andElectrochemichromic Materials and Phenomena,” in Non-emissiveElectrooptic Displays, A. Kmetz and K. von Willisen, eds. Plenum Press,New York, N.Y. 1976, pp. 155-196 (1976) and in various parts ofElectrochromism, P. M. S. Monk, R. J. Mortimer, D. R. Rosseinsky, VCHPublishers, Inc., New York, N.Y. (1995). Numerous electrochromic devicesare known in the art. See, e.g., Manos, U.S. Pat. No. 3,451,741;Bredfeldt et al., U.S. Pat. No. 4,090,358; Clecaket al., U.S. Pat. No.4,139,276; Kissa et al., U.S. Pat. No. 3,453,038; Rogers, U.S. Pat. Nos.3,652,149, 3,774,988 and 3,873,185; and Jones et al., U.S. Pat. Nos.3,282,157, 3,282,158, 3,282,160 and 3,283,656.

In addition to these devices, there are commercially availableelectrochromic devices and associated circuitry, such as those disclosedin U.S. Pat. No. 4,902,108, entitled “SINGLE-COMPARTMENT, SELF-ERASING,SOLUTION-PHASE ELECTROCHROMIC DEVICES SOLUTIONS FOR USE THEREIN, ANDUSES THEREOF,” issued Feb. 20, 1990, to H. J. Byker; Canadian Patent No.1,300,945, entitled “AUTOMATIC REARVIEW MIRROR SYSTEM FOR AUTOMOTIVEVEHICLES,” issued May 19, 1992, to J. H. Bechtel et al.; U.S. Pat. No.5,128,799, entitled “VARIABLE REFLECTANCE MOTOR VEHICLE MIRROR,” issuedJul. 7, 1992, to H. J. Byker; U.S. Pat. No. 5,202,787, entitled“ELECTRO-OPTIC DEVICE,” issued Apr. 13, 1993, to H. J. Byker et al.;U.S. Pat. No. 5,204,778, entitled “CONTROL SYSTEM FOR AUTOMATIC REARVIEWMIRRORS,” issued Apr. 20, 1993, to J. H. Bechtel; U.S. Pat. No.5,278,693, entitled “TINTED SOLUTION-PHASE ELECTROCHROMIC MIRRORS,”issued Jan. 11, 1994, to D. A. Theiste et al.; U.S. Pat. No. 5,280,380,entitled “UV-STABILIZED COMPOSITIONS AND METHODS,” issued Jan. 18, 1994,to H. J. Byker; U.S. Pat. No. 5,282,077, entitled “VARIABLE REFLECTANCEMIRROR,” issued Jan. 25, 1994, to H. J. Byker; U.S. Pat. No. 5,294,376,entitled “BIPYRIDINIUM SALT SOLUTIONS,” issued Mar. 15, 1994, to H. J.Byker; U.S. Pat. No. 5,336,448, entitled “ELECTROCHROMIC DEVICES WITHBIPYRIDINIUM SALT SOLUTIONS,” issued Aug. 9, 1994, to H. J. Byker; U.S.Pat. No. 5,434,407, entitled “AUTOMATIC REARVIEW MIRROR INCORPORATINGLIGHT PIPE,” issued Jan. 18, 1995, to F. T. Bauer et al.; U.S. Pat. No.5,448,397, entitled “OUTSIDE AUTOMATIC REARVIEW MIRROR FOR AUTOMOTIVEVEHICLES,” issued Sep. 5, 1995, to W. L. Tonar; and U.S. Pat. No.5,451,822, entitled “ELECTRONIC CONTROL SYSTEM,” issued Sep. 19, 1995,to J. H. Bechtel et al. Each of these patents is commonly assigned withthe present invention and the disclosures of each, including thereferences contained therein, are hereby incorporated herein in theirentirety by reference. Such electrochromic devices may be utilized in afully integrated inside/outside rearview mirror system or as separateinside or outside rearview mirror systems.

FIG. 1 shows a typical electrochromic mirror device 10, having front andrear planar elements 12 and 16, respectively. A transparent conductivecoating 14 is placed on the rear face of the front element 12, andanother transparent conductive coating 18 is placed on the front face ofrear element 16. A reflector (20 a, 20 b and 20 c), typically comprisinga silver metal layer 20 a covered by a protective copper metal layer 20b, and one or more layers of protective paint 20 c, is disposed on therear face of the rear element 16. For clarity of description of such astructure, the front surface of the front glass element is sometimesreferred to as the first surface, and the inside surface of the frontglass element is sometimes referred to as the second surface. The insidesurface of the rear glass element is sometimes referred to as the thirdsurface, and the back surface of the rear glass element is sometimesreferred to as the fourth surface. The front and rear elements are heldin a parallel and spaced-apart relationship by seal 22, thereby creatinga chamber 26. The electrochromic medium 24 is contained in space 26. Theelectrochromic medium 24 is in direct contact with transparent electrodelayers 14 and 18, through which passes electromagnetic radiation whoseintensity is reversibly modulated in the device by a variable voltage orpotential applied to electrode layers 14 and 18 through clip contactsand an electronic circuit (not shown).

The electrochromic medium 24 placed in space 26 may includesurface-confined, electrode position-type or solution-phase-typeelectrochromic materials and combinations thereof. In an allsolution-phase medium, the electrochemical properties of the solvent,optional inert electrolyte, anodic materials, cathodic materials, andany other components that might be present in the solution arepreferably such that no significant electrochemical or other changesoccur at a potential difference which oxidizes anodic material andreduces the cathodic material other than the electrochemical oxidationof the anodic material, electrochemical reduction of the cathodicmaterial, and the self-erasing reaction between the oxidized form of theanodic material and the reduced form of the cathodic material.

In most cases, when there is no electrical potential difference betweentransparent conductors 14 and 18, the electrochromic medium 24 in space26 is essentially colorless or nearly colorless, and incoming light(I_(o)) enters through front element 12, passes through transparentcoating 14, electrochromic containing chamber 26, transparent coating18, rear element 16, and reflects off layer 20 a and travels backthrough the device and out front element 12. Typically, the magnitude ofthe reflected image (I_(R)) with no electrical potential difference isabout 45 percent to about 85 percent of the incident light intensity(I_(o)). The exact value depends on many variables outlined below, suchas, for example, the residual reflection (I′_(R)) from the front face ofthe front element, as well as secondary reflections from the interfacesbetween: the front element 12 and the front transparent electrode 14,the front transparent electrode 14 and the electrochromic medium 24, theelectrochromic medium 24 and the second transparent electrode 18, andthe second transparent electrode 18 and the rear element 16. Thesereflections are well known in the art and are due to the difference inrefractive indices between one material and another as the light crossesthe interface between the two. If the front element and the back elementare not parallel, then the residual reflectance (I′_(R)) or othersecondary reflections will not superimpose with the reflected image(I_(R)) from mirror surface 20 a, and a double image will appear (wherean observer would see what appears to be double (or triple) the numberof objects actually present in the reflected image).

There are minimum requirements for the magnitude of the reflected imagedepending in whether the electrochromic mirrors are placed on the insideor the outside of the vehicle. For example, according to currentrequirements from most automobile manufacturers, inside mirrorspreferably have a high end reflectivity of at least 70 percent, andoutside mirrors must have a high end reflectivity of at least 35percent.

Electrode layers 14 and 18 are connected to electronic circuitry whichis effective to electrically energize the electrochromic medium, suchthat when a potential is applied across the transparent conductors 14and 18, electrochromic medium in space 26 darkens, such that incidentlight (I_(o)) is attenuated as the light passes toward the reflector 20a and as it passes back through after being reflected. By adjusting thepotential difference between the transparent electrodes, such a devicecan function as a “gray-scale” device, with continuously variabletransmittance over a wide range. For solution-phase electrochromicsystems, when the potential between the electrodes is removed orreturned to zero, the device spontaneously returns to the same,zero-potential, equilibrium color and transmittance as the device hadbefore the potential was applied. Other electrochromic materials areavailable for making electrochromic devices. For example, theelectrochromic medium may include electrochromic materials that aresolid metal oxides, redox active polymers, and hybrid combinations ofsolution-phase and solid metal oxides or redox active polymers; however,the above-described solution-phase design is typical of most of theelectrochromic devices presently in use.

Even before a fourth surface reflector electrochromic mirror wascommercially available, various groups researching electrochromicdevices had discussed moving the reflector from the fourth surface tothe third surface. Such a design has advantages in that it should,theoretically, be easier to manufacture because there are fewer layersto build into a device, i.e., the third surface transparent electrode isnot necessary when there is a third surface reflector/electrode.Although this concept was described as early as 1966, no group hadcommercial success because of the exacting criteria demanded from aworkable auto-dimming mirror incorporating a third surface reflector.U.S. Pat. No. 3,280,701, entitled “OPTICALLY VARIABLE ONE-WAY MIRROR,”issued Oct. 25, 1966, to J. F. Donnelly et al. has one of the earliestdiscussions of a third surface reflector for a system using a pH-inducedcolor change to attenuate light.

U.S. Pat. No. 5,066,112, entitled “PERIMETER COATED, ELECTRO-OPTICMIRROR,” issued Nov. 19, 1991, to N. R. Lynam et al., teaches anelectro-optic mirror with a conductive coating applied to the perimeterof the front and rear glass elements for concealing the seal. Although athird surface reflector is discussed therein, the materials listed asbeing useful as a third surface reflector suffer from one or more of thefollowing deficiencies: not having sufficient reflectivity for use as aninside mirror, or not being stable when in contact with a solution-phaseelectrochromic medium containing at least one solution-phaseelectrochromic material.

Others have broached the topic of a reflector/electrode disposed in themiddle of an all solid state-type device. For example, U.S. Pat. Nos.4,762,401, 4,973,141, and 5,069,535 to Baucke et al. teach anelectrochromic mirror having the following structure: a glass element, atransparent (ITO) electrode, a tungsten oxide electrochromic layer, asolid ion conducting layer, a single layer hydrogen ion-permeablereflector, a solid ion conducting layer, a hydrogen ion storage layer, acatalytic layer, a rear metallic layer, and a back element (representingthe conventional third and fourth surface). The reflector is notdeposited on the third surface and is not directly in contact withelectrochromic materials, certainly not at least one solution-phaseelectrochromic material and associated medium. Consequently, it isdesirable to provide an improved high reflectivity electrochromicrearview mirror having a third surface reflector/electrode in contactwith a solution-phase electrochromic medium containing at least oneelectrochromic material.

In the past, information, images or symbols from displays, such asvacuum fluorescent displays, have been displayed on electrochromicrearview mirrors for motor vehicles with reflective layers on the fourthsurface of the mirror. The display is visible to the vehicle occupant byremoving all of the reflective layer on a portion of the fourth surfaceand placing the display in that area. Although this design worksadequately due to the transparent conductors on the second and thirdsurface to impart current to the electrochromic medium, presently nodesign is commercially available which allows a display device to beincorporated into a mirror that has a reflective layer on the thirdsurface. Removing all of the reflective layer on the third surface inthe area aligned with the display area or the glare sensor area causessevere residual color problems when the electrochromic medium darkensand clears because, although colorization occurs at the transparentelectrode on the second surface, there is no corresponding electrode onthe third surface in that corresponding area to balance the charge. As aresult, the color generated at the second surface (across from thedisplay area or the glare sensor area) will not darken or clear at thesame rate as other areas with balanced electrodes. This color variationis significant and is very aesthetically unappealing to the vehicleoccupants.

Similar problems exist for outside rearview mirror assemblies thatinclude signal lights, such as turn signal lights, behind the rearsurface of the mirror. Examples of such signal mirrors are disclosed inU.S. Pat. Nos. 5,207,492, 5,361,190, and 5,788,357. By providing a turnsignal light in an outside mirror assembly, a vehicle, or other vehiclestraveling in the blind spot of the subject vehicle, will be more likelyto notice when the driver has activated the vehicle's turn signal andthereby attempt to avoid an accident. Such mirror assemblies typicallyemploy a dichroic mirror and a plurality of red LEDs mounted behind themirror as the signal light source. The dichroic mirror includes a glasssubstrate and a dichroic reflective coating provided on the rear surfaceof the glass plate that transmits the red light generated by the LEDs aswell as infrared radiation while reflecting all light and radiationhaving wavelengths less than that of red light. By utilizing a dichroicmirror, such mirror assemblies hide the LEDs when not in use to providethe general appearance of a typical rearview mirror, and allow the redlight from such LEDs to pass through the dichroic mirror and be visibleto drivers of vehicles behind and to the side of the vehicle in whichsuch a mirror assembly is mounted. Examples of such signal mirrors aredisclosed in U.S. Pat. Nos. 5,361,190 and 5,788,357.

In daylight, the intensity of the LEDs must be relatively high to enablethose in other vehicles to readily notice the signal lights. Because theimage reflected toward the driver is also relatively high in daylight,the brightness of the LEDs is not overly distracting. However, at nightthe same LED intensity could be very distracting, and hence, potentiallyhazardous. To avoid this problem, a day/night sensing circuit is mountedin the signal light subassembly behind the dichroic mirror to sensewhether it is daytime or nighttime and toggle the intensity of the LEDsbetween two different intensity levels. The sensor employed in theday/night sensing circuit is most sensitive to red and infrared light soas to more easily distinguish between daylight conditions and the brightglare from the headlights of a vehicle approaching from the rear. Hence,the sensor may be mounted behind the dichroic coating on the dichroicmirror.

The dichroic mirrors used in the above-described outside mirrorassemblies suffer from the same problems of many outside mirrorassemblies in that their reflectance cannot be dynamically varied toreduce nighttime glare from the headlights of other vehicles.

Although outside mirror assemblies exist that include signal lights andother outside mirror assemblies exist that include electrochromicmirrors, signal lights have not been provided in mirror assemblieshaving an electrochromic mirror because the dichroic coating needed tohide the LEDs of the signal light typically cannot be applied to anelectrochromic mirror, particularly those mirrors that employ a thirdsurface reflector/electrode.

SUMMARY OF THE INVENTION

Accordingly, it is an aspect of the present invention to solve the aboveproblems by providing an electrochromic rearview mirror assembly thatincludes a third surface reflector/electrode that provides a continuouslayer of electrically conductive material across the entire visiblesurface of the rear element of the mirror, even those regions that liein front of a light source, such as a signal light, information display,or illuminator, or a light sensor or receptor, that is positioned behindthe electrochromic mirror. Yet another aspect of the present inventionis to provide an electrochromic mirror having a third surfacereflector/electrode that is at least partially transmissive at least inregions in front of a light source, such as a display, illuminator, orsignal light. An additional aspect of the present invention is toprovide a third surface reflector/electrode (i.e., second electrode)that is at least partially reflective in those regions in front of thelight source so as to provide an ascetically pleasing appearance. Stillanother aspect of the present invention is to provide a coating for thethird surface of an electrochromic mirror that functions as an electrodeand as a reflector while allowing light having wavelengths correspondingto a display to be transmitted through the mirror. Still another aspectof the present invention is to provide an electrochromic mirror having apartially reflective, partially transmissive electrode that does nothave too yellow a hue and has relative color neutrality.

To achieve these and other aspects and advantages, the electrochromicmirror according to the present invention comprises front and rearelements having front and rear surfaces and being sealably bondedtogether in a spaced-apart relationship to define a chamber; atransparent first electrode including a layer of conductive materialcarried on a surface of one of the elements; an electrochromic materialcontained in the chamber; and a partially transmissive, partiallyreflective second electrode disposed over substantially all of the frontsurface of the rear element. The electrochromic rearview mirror soconstructed, has a reflectance of at least about 35% and a transmittanceof at least about 5% in at least portions of the visible spectrum. Themirror preferably further exhibits relative color neutrality with a C*value of less than about 20. Further, the mirror preferably does nothave a perceivable yellow hue and thus has a b* value less than about15.

Another aspect of the present invention is to provide a rearview mirrorassembly having a light emitting display assembly mounted behind themirror within the mirror housing whereby spurious reflections and ghostimages are substantially reduced or eliminated. To achieve this andother aspects and advantages, a rearview mirror assembly according tothe present invention comprises a housing adapted to be mounted to thevehicle; front and rear elements mounted in the housing, the elementseach having front and rear surfaces and being sealably bonded togetherin a spaced-apart relationship to define a chamber; an electrochromicmaterial contained in the chamber; a transparent first electrodeincluding a layer of conductive material carried on a surface of one ofthe elements; a second electrode disposed on the front surface of therear element; and a light emitting display mounted in the housing.Either the second electrode is reflective or a separate reflector isprovided on the rear surface of the rear element, the reflectiveelectrode/reflector being at least partially transmissive in at least alocation in front of the display. The display has a front surface and ispreferably mounted behind the rear surface of the rear element, suchthat the front surface of the display is not parallel with the rearsurface of the mirror. Alternatively, the display may have anon-specular front surface or the front surface could be laminateddirectly onto the back of the mirror. As yet another alternative, ananti-reflection coating may be applied to the reflective surface(s) ofthe display and the front surface of the mirror. Still anotheralternative to achieve the above aspects and advantages is to provide atleast one masking component that minimizes light that is emitted fromthe display from reflecting off of the reflector back toward the displayand then reflecting back off the front surface of the display toward thefront surface of the front element then on to the viewer.

An additional aspect of the present invention is to provide a rearviewmirror assembly including a light emitting display, whereby the displayis mounted in front of the reflective layer of the mirror. To achievethese and other aspects of the present invention, a light emittingdisplay may be used that is substantially transparent and mounted eitherto the front surface of the front element or mounted in the chamberdefined between the front and rear elements. A preferred transparentlight emitting display is an organic light emitting diode display.

Another aspect of the present invention is to provide an exteriorrearview mirror assembly incorporating a light source for illuminating aportion of the exterior of the vehicle, such as the door handle andlocking mechanism area of a vehicle door. To achieve these and otheraspects and advantages, an exterior rearview mirror assembly of thepresent invention comprises a housing adapted to be mounted to theexterior of the vehicle; a first element mounted in the housing, theelement having a front and rear surface; a reflector disposed on one ofthe surfaces of the first element; and a light source mounted in thehousing behind the rear surface of the first element, the light sourcebeing positioned within the housing so as to emit light, when activated,through the first element and through a region of the reflector that isat least partially transmissive toward a side of a vehicle. Such arearview mirror assembly thus conveniently illuminates areas on theoutside of the vehicle such as the door handles and locking mechanisms.

Another aspect of the invention is to locate a light sensor, such asthat used to sense ambient light in an electrochromic mirror assembly,behind a reflective portion of the mirror while providing for increasedsensing area for light collection behind the electrochromic media andreflective portion of the mirror without the distractive appearanceresulting from missing patches of reflective material in the mirror. Toachieve these and other aspects and advantages, an electrochromic mirrorof the present invention comprises a housing adapted to be mounted tothe vehicle; front and rear elements mounted in said housing, theelements each having front and rear surfaces and being sealably bondedtogether in a spaced-apart relationship to define a chamber; atransparent first electrode including a layer of conductive materialcarried on a surface of one of the elements; a second electrode disposedon the front surface of the rear element, wherein either said secondelectrode is a reflective electrode or a separate reflector is disposedover substantially all of the rear surface of the rear element, thereflective electrode/reflector being partially transmissive andpartially reflective over substantially all of one of the surfaces ofthe rear element; an electrochromic material contained in the chamber;and a light sensor mounted in the housing behind the rear element andbehind the partially transmissive, partially reflectiveelectrode/reflector.

In accordance with another embodiment of the present invention, arearview mirror assembly for a vehicle comprises: a housing adapted tobe mounted to the vehicle; front and rear elements mounted in thehousing, the elements each having front and rear surfaces and beingsealably bonded together in a spaced-apart relationship to define achamber; a transparent first electrode including a layer of conductivematerial carried on a surface of one of the elements; a second electrodedisposed on the front surface of the rear element; an electrochromicmaterial contained in the chamber; and a graphic display positioned inthe housing behind said rear element, wherein either the secondelectrode is a reflective electrode or a separate reflector is disposedover substantially all of the rear surface of the rear element, thereflective electrode/reflector being partially transmissive andpartially reflective in at least a location in front of the graphicdisplay.

These and other features, advantages, and objects of the presentinvention will be further understood and appreciated by those skilled inthe art by reference to the following specification, claims, andappended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is an enlarged cross-sectional view of a prior art electrochromicmirror assembly;

FIG. 2 is a front elevational view schematically illustrating aninside/outside electrochromic rearview mirror system for motor vehicles,where the inside and outside mirrors incorporate the mirror assembly ofthe present invention;

FIG. 3 is an enlarged cross-sectional view of the inside electrochromicrearview mirror incorporating a third surface reflector/electrodeillustrated in FIG. 2, taken on the line 3-3′ thereof;

FIG. 4 is an enlarged cross-sectional view of an electrochromic mirrorincorporating an alternate embodiment of a third surfacereflector/electrode according to the present invention;

FIG. 5 a is an enlarged cross-sectional view of an electrochromic mirrorhaving an improved arrangement for applying a drive potential to thetransparent conductor on the second surface of the mirror;

FIG. 5 b is an enlarged top view of the third surface reflector of FIG.5 a;

FIG. 6 is an enlarged cross-sectional view of an electrochromic mirrorusing a cured and machine-milled epoxy seal to hold the transparentelements in a spaced-apart relationship;

FIGS. 7A-7G are partial cross-sectional views of alternativeconstructions of the electrochromic mirror according to the presentinvention as taken along line 7-7′ shown in FIG. 2;

FIG. 8 is a partial cross-sectional view of the electrochromic mirroraccording to the present invention as taken along line 7-7′ shown inFIG. 2;

FIGS. 9A-9E are partial cross-sectional views of additional alternativeconstructions of the electrochromic mirror according to the presentinvention as taken along lines 7-7′ shown in FIG. 2;

FIG. 10 is a front elevational view schematically illustrating an insideelectrochromic rearview mirror incorporating the mirror assembly of thepresent invention;

FIG. 11 is a partial cross-sectional view of the electrochromic mirrorshown in FIG. 10 taken along line 11-11′;

FIG. 12 is a perspective view of an outside automatic rearview mirrorincluding a signal light and an electrical circuit diagram in block formof an outside rearview mirror assembly constructed in accordance withthe present invention;

FIG. 13 is a front elevational view of a signal light subassembly thatmay be used in the outside mirror assembly of the present invention;

FIG. 14A is a partial cross-sectional view taken along line 14-14′ ofFIG. 12 illustrating one construction of the outside rearview mirror ofthe present invention;

FIG. 14B is a partial cross-sectional view taken along line 14-14′ ofFIG. 12 illustrating a second alternative arrangement of the outsiderearview mirror constructed in accordance with the second embodiment ofthe present invention;

FIG. 14C is a partial cross-sectional view taken along lines 14-14′ ofFIG. 12 illustrating a third alternative arrangement of the outsiderearview mirror constructed in accordance with the second embodiment ofthe present invention;

FIG. 14D is a partial cross-sectional view taken along lines 14-14′ ofFIG. 12 illustrating a fourth alternative arrangement of the outsiderearview mirror constructed in accordance with another embodiment of thepresent invention;

FIG. 15 is a pictorial representation of two vehicles, one of whichincludes the signal mirror of the present invention;

FIG. 16 is a front elevational view of an automatic rearview mirrorembodying the information display area of another embodiment of thepresent invention;

FIG. 17 is an enlarged cross-sectional view, with portions broken awayfor clarity of illustration, of the automatic rearview mirrorillustrated in FIG. 16;

FIG. 18 is a front elevational view of the information display area,with portions broken away for clarity of illustration, of the automaticrearview mirror illustrated in FIG. 16;

FIG. 19 is a perspective view of a signal light assembly for use withanother embodiment of the present invention;

FIG. 20 is a front elevational view of an outside rearview mirrorassembly constructed in accordance with another embodiment of thepresent invention;

FIG. 21 is a partial cross-sectional view of the rearview mirrorassembly shown in FIG. 20 taken along line 21-21′;

FIG. 22 is a perspective view of an exterior portion of an exemplaryvehicle embodying the outside rearview mirror of the present inventionas illustrated in FIGS. 20 and 21;

FIG. 23A is a front perspective view of a mask bearing indicia inaccordance with another aspect of the present invention;

FIG. 23B is a front perspective view of a rearview mirror constructed inaccordance with another aspect of the present invention;

FIG. 24 is a front perspective view of a circuit board containing aplurality of light sources arranged in a configuration useful as adisplay in accordance with one aspect of the present invention;

FIG. 25 is a cross-sectional view of a display and mirror constructed inaccordance with one aspect of the present invention;

FIG. 26 is a schematic diagram of a vehicle sensor and display system inaccordance with an embodiment of the present invention;

FIG. 27 is a front elevational view of a rearview mirror including apassenger air bag status display in accordance with an embodiment of thepresent invention;

FIG. 28 is a partially schematic, side-sectional view illustrating arearview mirror display in accordance with an embodiment of the presentinvention;

FIG. 29 is a front elevational view of a rearview mirror including anon-planar display in accordance with another embodiment of the presentinvention;

FIG. 30 is a bottom view of the rearview mirror of FIG. 29;

FIG. 31 is a side view of the rearview mirror of FIG. 29;

FIG. 32 is a front elevational view of a rearview mirror including anon-planar display in accordance with a further embodiment of thepresent invention;

FIG. 33 is a bottom view of the rearview mirror of FIG. 32;

FIG. 34 is a front elevational view of a rearview mirror including anon-planar display in accordance with another embodiment of the presentinvention;

FIG. 35 is a top view of the rearview mirror of FIG. 34;

FIG. 36 is a front elevational view of a rearview mirror including anon-planar display in accordance with a further embodiment of thepresent invention;

FIG. 37 is a top view of the rearview mirror of FIG. 36;

FIG. 38 is a partially schematic, side-sectional view illustrating arearview mirror display in accordance with an embodiment of the presentinvention;

FIGS. 39 and 40 are front and bottom views of another embodiment of thepresent invention, including a particularly shaped indicia panel;

FIG. 41 is a cross section taken along the line XVI-XVI in FIG. 39;

FIGS. 42 and 43 are front and rear exploded perspective views of themirror shown in FIG. 39;

FIG. 44 is a front view of the indicia panel shown in FIG. 39;

FIGS. 45 and 46 are rear and side views of the indicia panel shown inFIG. 44;

FIG. 47 is a cross section taken along the line XXII-XXII in FIG. 45;

FIG. 48 is an exploded perspective view of the indicia panel shown inFIG. 44;

FIG. 49 is a flow chart showing a manufacturing method for assemblingthe mirror shown in FIG. 39;

FIG. 50 is a schematic side cross section similar to FIG. 28, butshowing undesirable secondary light reflections in the embodiment ofFIG. 39; and

FIG. 51 is a schematic side cross section similar to FIG. 50, butshowing an embodiment where the indicia panel is attached to a front ofthe mirror subassembly and under the front bezel.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 2 shows a front elevational view schematically illustrating aninside mirror assembly 110 and two outside rearview mirror assemblies111 a and 111 b for the driver-side and passenger-side, respectively,all of which are adapted to be installed on a motor vehicle in aconventional manner and where the mirrors face the rear of the vehicleand can be viewed by the driver of the vehicle to provide a rearwardview. Inside mirror assembly 110 and outside rearview mirror assemblies111 a and 111 b may incorporate light-sensing electronic circuitry ofthe type illustrated and described in the above-referenced CanadianPatent No. 1,300,945, U.S. Pat. No. 5,204,778, or U.S. Pat. No.5,451,822, and other circuits capable of sensing glare and ambient lightand supplying a drive voltage to the electrochromic element. Mirrorassemblies 110, 111 a, and 111 b are essentially identical in that likenumbers identify components of the inside and outside mirrors. Thesecomponents may be slightly different in configuration, but function insubstantially the same manner and obtain substantially the same resultsas similarly numbered components. For example, the shape of the frontglass element of inside mirror 110 is generally longer and narrower thanoutside mirrors 111 a and 111 b. There are also some differentperformance standards placed on inside mirror 110 compared with outsidemirrors 111 a and 111 b. For example, inside mirror 110 generally, whenfully cleared, should have a reflectance value of about 70 percent toabout 85 percent or higher, whereas the outside mirrors often have areflectance of about 50 percent to about 65 percent. Also, in the UnitedStates (as supplied by the automobile manufacturers), the passenger-sidemirror 111 b typically has a spherically bent or convex shape, whereasthe driver-side mirror 111 a and inside mirror 110 presently must beflat. In Europe, the driver-side mirror 111 a is commonly flat oraspheric, whereas the passenger-side mirror 111 b has a convex shape. InJapan, both outside mirrors have a convex shape. The followingdescription is generally applicable to all mirror assemblies of thepresent invention.

FIG. 3 shows a cross-sectional view of mirror assembly 110 having afront transparent element 112 having a front surface 112 a and a rearsurface 112 b, and a rear element 114 having a front surface 114 a and arear surface 114 b. For clarity of description of such a structure, thefollowing designations will be used hereinafter. The front surface 112 aof the front glass element will be referred to as the first surface, andthe back surface 112 b of the front glass element as the second surface.The front surface 114 a of the rear glass element will be referred to asthe third surface, and the back surface 114 b of the rear glass elementas the fourth surface. A chamber 125 is defined by a layer oftransparent conductor 128 (carried on second surface 112 b), areflector/electrode 120 (disposed on third surface 114 a), and an innercircumferential wall 132 of sealing member 116. An electrochromic medium126 is contained within chamber 125.

As broadly used and described herein, the reference to an electrode orlayer as being “carried” on a surface of an element, refers to bothelectrodes or layers that are disposed directly on the surface of anelement or disposed on another coating, layer or layers that aredisposed directly on the surface of the element.

Front transparent element 112 may be any material which is transparentand has sufficient strength to be able to operate in the conditions,e.g., varying temperatures and pressures, commonly found in theautomotive environment. Front element 112 may comprise any type ofborosilicate glass, soda lime glass, float glass, or any other material,such as, for example, a polymer or plastic, that is transparent in thevisible region of the electromagnetic spectrum. Front element 112 ispreferably a sheet of glass. The rear element must meet the operationalconditions outlined above, except that it does not need to betransparent in all applications, and therefore may comprise polymers,metals, glass, ceramics, and preferably is a sheet of glass.

The coatings of the third surface 114 a are sealably bonded to thecoatings on the second surface 112 b in a spaced-apart and parallelrelationship by a seal member 116 disposed near the outer perimeter ofboth second surface 112 b and third surface 114 a. Seal member 116 maybe any material that is capable of adhesively bonding the coatings onthe second surface 112 b to the coatings on the third surface 114 a toseal the perimeter such that electrochromic material 126 does not leakfrom chamber 125. Optionally, the layer of transparent conductivecoating 128 and the layer of reflector/electrode 120 may be removed overa portion where the seal member is disposed (not the entire portion,otherwise the drive potential could not be applied to the two coatings).In such a case, seal member 116 must bond well to glass.

The performance requirements for a perimeter seal member 116 used in anelectrochromic device are similar to those for a perimeter seal used ina liquid crystal device (LCD), which are well known in the art. The sealmust have good adhesion to glass, metals and metal oxides; must have lowpermeabilities for oxygen, moisture vapor, and other detrimental vaporsand gases; and must not interact with or poison the electrochromic orliquid crystal material it is meant to contain and protect. Theperimeter seal can be applied by means commonly used in the LCDindustry, such as by silk-screening or dispensing. Totally hermeticseals, such as those made with glass fit or solder glass, can be used,but the high temperatures involved in processing (usually near 450° C.)this type of seal can cause numerous problems, such as glass substratewarpage, changes in the properties of transparent conductive electrode,and oxidation or degradation of the reflector. Because of their lowerprocessing temperatures, thermoplastic, thermosetting or UV curingorganic sealing resins are preferred. Such organic resin sealing systemsfor LCDs are described in U.S. Pat. Nos. 4,297,401, 4,418,102,4,695,490, 5,596,023, and 5,596,024. Because of their excellent adhesionto glass, low oxygen permeability and good solvent resistance,epoxy-based organic sealing resins are preferred. These epoxy resinseals may be UV curing, such as described in U.S. Pat. No. 4,297,401, orthermally curing, such as with mixtures of liquid epoxy resin withliquid polyamide resin or dicyandiamide, or they can be homopolymerized.The epoxy resin may contain fillers or thickeners to reduce flow andshrinkage such as fumed silica, silica, mica, clay, calcium carbonate,alumina, etc., and/or pigments to add color. Fillers pretreated withhydrophobic or silane surface treatments are preferred. Cured resincrosslink density can be controlled by use of mixtures ofmono-functional, di-functional, and multi-functional epoxy resins andcuring agents. Additives such as silanes or titanates can be used toimprove the seal's hydrolytic stability, and spacers such as glass beadsor rods can be used to control final seal thickness and substratespacing. Suitable epoxy resins for use in a perimeter seal member 116include, but are not limited to: “EPON RESIN” 813, 825, 826, 828, 830,834, 862, 1001F, 1002F, 2012, DPS-155, 164, 1031, 1074, 58005, 58006,58034, 58901, 871, 872, and DPL-862 available from Shell Chemical Co.,Houston, Tex.; “ARALITE” GY 6010, GY 6020, CY 9579, GT 7071, XU 248, EPN1139, EPN 1138, PY 307, ECN 1235, ECN 1273, ECN 1280, MT 0163, MY 720,MY 0500, MY 0510, and PT 810 available from Ciba Geigy, Hawthorne, N.Y.;and “D.E.R.” 331, 317, 361, 383, 661, 662, 667, 732, 736, “D.E.N.” 431,438, 439 and 444 available from Dow Chemical Co., Midland, Mich.Suitable epoxy curing agents include V-15, V-25, and V-40 polyamidesfrom Shell Chemical Co.; “AJICURE” PN-23, PN-34, and VDH available fromAjinomoto Co., Tokyo, Japan; “CUREZOL” AW, 2MZ, 2E4MZ, C11Z, C17Z, 2PZ,2IZ, and 2P4MZ available from Shikoku Fine Chemicals, Tokyo, Japan;“ERISYS” DDA or DDA accelerated with U-405, 24EMI, U-410, and U-415available from CVC Specialty Chemicals, Maple Shade, N.J.; and “AMICURE”PACM, 352, CG, CG-325, and CG-1200 available from Air Products,Allentown, Pa. Suitable fillers include fumed silica such as “CAB-O-SIL”L-90, LM-130, LM-5, PTG, M-5, MS-7, MS-55, TS-720, HS-5, and EH-5available from Cabot Corporation, Tuscola, Ill.; “AEROSIL” R972, R974,R805, R812, R812 S, R202, US204, and US206 available from Degussa,Akron, Ohio. Suitable clay fillers include BUCA, CATALPO, ASP NC,SATINTONE 5, SATINTONE SP-33, TRANSLINK 37, TRANSLINK 77, TRANSLINK 445,and TRANSLINK 555 available from Engelhard Corporation, Edison, N.J.Suitable silica fillers are SILCRON G-130, G-300, G-100-T, and G-100available from SCM Chemicals, Baltimore, Md. Suitable silane couplingagents to improve the seal's hydrolytic stability are Z-6020, Z-6030,Z-6032, Z-6040, Z-6075, and Z-6076 available from Dow CorningCorporation, Midland, Mich. Suitable precision glass microbead spacersare available in an assortment of sizes from Duke Scientific, Palo Alto,Calif.

The layer of a transparent electrically conductive material 128 isdeposited on the second surface 112 b to act as an electrode.Transparent conductive material 128 may be any material which bonds wellto front element 112, is resistant to corrosion to any materials withinthe electrochromic device, resistant to corrosion by the atmosphere, hasminimal diffuse or specular reflectance, high light transmission, nearneutral coloration, and good electrical conductance. Transparentconductive material 128 may be fluorine-doped tin oxide, doped zincoxide, zinc-doped indium oxide, indium tin oxide (ITO), ITO/metal/ITO(IMI) as disclosed in “Transparent Conductive Multilayer-Systems for FPDApplications,” by J. Stollenwerk, B. Ocker, K. H. Kretschmer of LEYBOLDA G, Alzenau, Germany, the materials described in above-referenced U.S.Pat. No. 5,202,787, such as TEC 20 or TEC 15, available from LibbeyOwens-Ford Co. of Toledo, Ohio, or other transparent conductors.Generally, the conductance of transparent conductive material 128 willdepend on its thickness and composition. IMI generally has superiorconductivity compared with the other materials. IMI is, however, knownto undergo more rapid environmental degradation and suffer frominterlayer delamination. The thickness of the various layers in the IMIstructure may vary, but generally the thickness of the first ITO layerranges from about 10 Å to about 200 Å, the metal ranges from about 10 Åto about 200 Å, and the second layer of ITO ranges from about 10 Å toabout 200 Å. If desired, an optional layer or layers of a colorsuppression material 130 may be deposited between transparent conductivematerial 128 and the second surface 112 b to suppress the reflection ofany unwanted portions of the electromagnetic spectrum.

In accordance with the present invention, a combinationreflector/electrode 120 is disposed on third surface 114 a.Reflector/electrode 120 comprises at least one layer of a reflectivematerial 121 which serves as a mirror reflectance layer and also formsan integral electrode in contact with and in a chemically andelectrochemically stable relationship with any constituents in anelectrochromic medium. As stated above, the conventional method ofbuilding electrochromic devices was to incorporate a transparentconductive material on the third surface as an electrode, and place areflector on the fourth surface. By combining the “reflector” and“electrode” and placing both on the third surface, several unexpectedadvantages arise which not only make the device manufacture lesscomplex, but also allow the device to operate with higher performance.The following will outline the exemplary advantages of the combinedreflector/electrode of the present invention.

First, the combined reflector/electrode 120 on the third surfacegenerally has higher conductance than a conventional transparentelectrode and previously used reflector/electrodes, which will allowgreater design flexibility. One can either change the composition of thetransparent conductive electrode on the second surface to one that haslower conductance (being cheaper and easier to produce and manufacture)while maintaining coloration speeds similar to that obtainable with afourth surface reflector device, while at the same time decreasingsubstantially the overall cost and time to produce the electrochromicdevice. If, however, performance of a particular design is of utmostimportance, a moderate to high conductance transparent electrode can beused on the second surface, such as, for example, ITO, IMI, etc. Thecombination of a high conductance (i.e., less than 250Ω/Y, preferablyless than 15Ω/Y) reflector/electrode on the third surface and a highconductance transparent electrode on the second surface will not onlyproduce an electrochromic device with more even overall coloration, butwill also allow for increased speed of coloration and clearing.Furthermore, in fourth surface reflector mirror assemblies there are twotransparent electrodes with relatively low conductance, and inpreviously used third surface reflector mirrors there is a transparentelectrode and a reflector/electrode with relatively low conductance and,as such, a long buss bar on the front and rear element to bring currentin and out is necessary to ensure adequate coloring speed. The thirdsurface reflector/electrode of the present invention has a higherconductance and therefore has a very even voltage or potentialdistribution across the conductive surface, even with a small orirregular contact area. Thus, the present invention provides greaterdesign flexibility by allowing the electrical contact for the thirdsurface electrode to be very small while still maintaining adequatecoloring speed.

Second, a third surface reflector/electrode helps improve the imagebeing viewed through the mirror. FIG. 1 shows how light travels througha conventional fourth surface reflector device. In the fourth surfacereflector, the light travels through: the first glass element, thetransparent conductive electrode on the second surface, theelectrochromic media, the transparent conductive electrode on the thirdsurface, and the second glass element, before being reflected by thefourth surface reflector. Both transparent conductive electrodes exhibithighly specular transmittance but also possess diffuse transmittance andreflective components, whereas the reflective layer utilized in anyelectrochromic mirror is chosen primarily for its specular reflectance.By diffuse reflectance or transmittance component, we mean a materialwhich reflects or transmits a portion of any light impinging on itaccording to Lambert's law whereby the light rays are spread-about orscattered. By specular reflectance or transmittance component, we mean amaterial which reflects or transmits light impinging on it according toSnell's laws of reflection or refraction. In practical terms, diffusereflectors and transmitters tend to slightly blur images, whereasspecular reflectors show a crisp, clear image. Therefore, lighttraveling through a mirror having a device with a fourth surfacereflector has two partial diffuse reflectors (on the second and thirdsurface) which tend to blur the image, and a device with a third surfacereflector/electrode of the present invention only has one diffusereflector (on the second surface).

Additionally, because the transparent electrodes act as partial diffusetransmitters, and the farther away the diffuse transmitter is from thereflecting surface the more severe the blurring becomes, a mirror with afourth surface reflector appears significantly more hazy than a mirrorwith a third surface reflector. For example, in the fourth surfacereflector shown in FIG. 1, the diffuse transmitter on the second surfaceis separated from the reflector by the electrochromic material, thesecond conductive electrode, and the second glass element. The diffusetransmitter on the third surface is separated from the reflector by thesecond glass element. By incorporating a combined reflector/electrode onthe third surface in accordance with the present invention, one of thediffuse transmitters is removed, and the distance between the reflectorand the remaining diffuse transmitter is closer by the thickness of therear glass element. Therefore, the third surface metalreflector/electrode of the present invention provides an electrochromicmirror with a superior viewing image.

Finally, a third surface metal reflector/electrode improves the abilityto reduce double imaging in an electrochromic mirror. As stated above,there are several interfaces where reflections can occur. Some of thesereflections can be significantly reduced with color suppression oranti-reflective coatings; however, the most significant “double imaging”reflections are caused by misalignment of the first surface and thesurface containing the reflector, and the most reproducible way ofminimizing the impact of this reflection is by ensuring both glasselements are parallel. Presently, convex glass is often used for thepassenger side outside mirror and aspheric glass is sometimes used forthe driver side outside mirror to increase the field of view and reducepotential blind spots. However, it is difficult to reproducibly bendsuccessive elements of glass having identical radii of curvature.Therefore, when building an electrochromic mirror, the front glasselement and the rear glass element may not be perfectly parallel (do nothave identical radii of curvature), and therefore, the otherwisecontrolled double imaging problems become much more pronounced. Byincorporating a combined reflector electrode on the third surface of thedevice in accordance with the present invention, light does not have totravel through the rear glass element before being reflected, and anydouble imaging that occurs from the elements being out of parallel willbe significantly reduced.

It is desirable in the construction of outside rearview mirrors toincorporate thinner glass in order to decrease the overall weight of themirror so that the mechanisms used to manipulate the orientation of themirror are not overloaded. Decreasing the weight of the device alsoimproves the dynamic stability of the mirror assembly when exposed tovibrations. Heretofore, no electrochromic mirrors incorporating asolution-phase electrochromic medium and two thin glass elements havebeen commercially available, because thin glass suffers from beingflexible and prone to warpage or breakage, especially when exposed toextreme environments. This problem is substantially improved by using animproved electrochromic device incorporating two thin glass elementshaving an improved gel material. This improved device is disclosed incommonly assigned U.S. Pat. No. 5,940,201 entitled “AN ELECTROCHROMICMIRROR WITH TWO THIN GLASS ELEMENTS AND A GELLED ELECTROCHROMIC MEDIUM,”filed on or about Apr. 2, 1997. The entire disclosure, including thereferences contained therein, of this patent is incorporated herein byreference. The addition of the combined reflector/electrode onto thethird surface of the device further helps remove any residual doubleimaging resulting from the two glass elements being out of parallel.

The most important factors for obtaining a reliable electrochromicmirror having a third surface reflector/electrode 120 are that thereflector/electrode have sufficient reflectance and that the mirrorincorporating the reflector/electrode has adequate operational life.Regarding reflectance, the automobile manufacturers prefer a reflectivemirror for the inside mirror having a reflectivity of at least 60percent, whereas the reflectivity requirements for an outside mirror areless stringent and generally must be at least 35 percent.

To produce an electrochromic mirror with 70 percent reflectance, thereflector must have a reflectance higher than 70 percent because theelectrochromic medium in front of the reflector reduces the reflectancefrom the reflector interface as compared to having the reflector in airdue to the medium having a higher index of refraction as compared toair. Also, the glass, the transparent electrode, and the electrochromicmedium even in its clear state are slightly light absorbing. Typically,if an overall reflectance of 65 percent is desired, the reflector musthave a reflectance of about 75 percent.

Regarding operational life, the layer or layers that comprise thereflector/electrode 120 must have adequate bond strength to theperipheral seal, the outermost layer must have good shelf life betweenthe time it is coated and the time the mirror is assembled, the layer orlayers must be resistant to atmospheric and electrical contactcorrosion, and must bond well to the glass surface or to other layersdisposed beneath it, e.g., the base or intermediate layer (122 or 123,respectively). The overall sheet resistance for the reflector/electrode120 may range from about 0.01Ω/Y to about 100Ω/Y and preferably rangesfrom about 0.2Ω/Y to about 25Ω/Y. As will be discussed in more detailbelow, improved electrical interconnections using a portion of the thirdsurface reflector/electrode as a high conductance contact or buss barfor the second surface transparent conductive electrode may be utilizedwhen the conductance of the third surface reflector/electrode is belowabout 2Ω/Y.

Referring to FIG. 3 for one embodiment of the present invention, areflector/electrode that is made from a single layer of a reflectivesilver or silver alloy 121 is provided that is in contact with at leastone solution-phase electrochromic material. The layer of silver orsilver alloy covers the entire third surface 114 a of second element114. The reflective silver alloy means a homogeneous or non-homogeneousmixture of silver and one or more metals, or an unsaturated, saturated,or supersaturated solid solution of silver and one or more metals. Thethickness of reflective layer 121 ranges from about 50 Å to about 2000Å, and more preferably from about 200 Å to about 1000 Å. If reflectivelayer 121 is disposed directly to the glass surface, it is preferredthat the glass surface be treated by plasma discharge to improveadhesion.

Table 1 shows the relevant properties for a number of different metalsthat have been proposed for third surface reflectors as compared withthe materials suitable for the reflector/electrode 120 of the presentinvention. The only materials in Table 1 having reflectance propertiessuitable for use as a third surface reflector/electrode in contact withat least one solution-phase electrochromic material for an insideelectrochromic mirror for a motor vehicle are aluminum, silver, andsilver alloys. Aluminum performs very poorly when in contact withsolution-phase material(s) in the electrochromic medium because aluminumreacts with or is corroded by these materials. The reacted or corrodedaluminum is non-reflective and non-conductive and will typicallydissolve off, flake off, or delaminate from the glass surface. Silver ismore stable than aluminum but can fail when deposited over the entirethird surface because it does not have long shelf life and is notresistant to electrical contact corrosion when exposed to theenvironmental extremes found in the motor vehicle environment. Theseenvironmental extremes include temperatures ranging from about −40° C.to about 85° C., and humidities ranging from about 0 percent to about100 percent. Further, mirrors must survive at these temperatures andhumidities for coloration cycle lives up to 100,000 cycles. The otherprior art materials (silver/copper, chromium, stainless steel, rhodium,platinum, palladium, Inconel®, copper, or titanium) suffer from any oneof a number of deficiencies such as: very poor color neutrality(silver/copper and copper); poor reflectance (chromium, stainless steel,rhodium, molybdenum, platinum, palladium, Inconel®, and titanium); poorcleanability (chromium); or poor electrical contact stability (chromium,stainless steel and molybdenum).

When silver is alloyed with certain materials to produce a third surfacereflector/electrode, the deficiencies associated with silver metal andaluminum metal can be overcome. Suitable materials for the reflectivelayer are alloys of silver/palladium, silver/gold, silver/platinum,silver/rhodium, silver/titanium, etc. The amount of the solute material,i.e., palladium, gold, etc., can vary. As can be seen from Table 1, thesilver alloys surprisingly retain the high reflectance and low sheetresistance properties of silver, while simultaneously improving theircontact stability, shelf life, and also increasing their window ofpotential stability when used as electrodes in propylene carbonatecontaining 0.2 molar tetraethylammonium tetrafluoroborate. The presentlypreferred materials for reflective layer 121 are silver/gold,silver/platinum, and silver/palladium.

More typically, reflector/electrode 120 has, in addition to the layer ofa reflective alloy 121, an optional base layer of a conductive metal oralloy 122 deposited directly on the third surface 114 a. There may alsobe an optional intermediate layer of a conductive metal or alloy 123disposed between the layer of reflective material 121 and the base coat122. If reflector/electrode 120 includes more than one layer, thereshould not be galvanic corrosion between the two metals or alloys. Ifoptional base layer 122 is deposited between the reflective layer 121and the glass element 114, it should be environmentally rugged, e.g.,bond well to the third (glass) surface 114 a and to reflective layer121, and maintain this bond when the seal 116 is bonded to thereflective layer. Base layer 122 may have a thickness from about 50 Å toabout 2000 Å, and more preferably from about 100 Å to about 1000 Å.Suitable materials for the base layer 122 are chromium, stainless steel,titanium, and alloys of chromium/molybdenum/nickel, molybdenum, andnickel-based alloys (commonly referred to as Inconel®, available fromCastle Metals, Chicago, Ill.). The main constituents of Inconel® arenickel which may range from 52 percent to 76 percent (Inconel® 617 and600, respectfully), iron which may range from 1.5 percent to 18.5percent (Inconel® 617 and Inconel® 718, respectfully), and chromiumwhich may range from 15 percent to 23 percent (Inconel® 600 and Inconel®601, respectfully). Inconel® 617 having 52 percent nickel, 1.5 percentiron, 22 percent chromium, and typical “other” constituents including12.5 percent cobalt, 9.0 percent molybdenum, and 1.2 percent aluminumwas used in the present examples.

In some instances it is desirable to provide an optional intermediatelayer 123 between the reflective layer 121 and the base layer 122 incase the material of layer 121 does not adhere well to the material oflayer 122 or there are any adverse interactions between the materials,e.g., galvanic corrosion. If used, intermediate layer 123 should exhibitenvironmental ruggedness, e.g., bond well to the base layer 122 and tothe reflective layer 121, and maintain this bond when the seal member116 is bonded to the reflective layer 121. The thickness of intermediatelayer 123 ranges from about 10 Å to about 2000 Å, and more preferablyfrom about 100 Å to about 1000 Å. Suitable materials for the optionalintermediate layer 123 are molybdenum, rhodium, stainless steel,titanium, copper, nickel, gold, platinum, and alloys thereof. Referenceis made to examples 1 and 2 to show how the insertion of a rhodiumintermediate layer between a chromium base layer and a silver or silveralloy reflective layer increases the time to failure incopper-accelerated acetic acid-salt spray (CASS) by a factor of 10.Example 4 shows how the insertion of a molybdenum intermediate layerbetween a chromium base layer and a silver alloy having a molybdenumflash over-coat layer increases the time to failure in CASS by a factorof 12.

Finally, it is sometimes desirable to provide an optional flashover-coat 124 over reflective layer 121, such that it (and not thereflective layer 121) contacts the electrochromic medium. This flashover-coat layer 124 must have stable behavior as an electrode, it musthave good shelf life, it must bond well to the reflective layer 121, andmaintain this bond when the seal member 116 is bonded thereto. It mustbe sufficiently thin, such that it does not completely block thereflectivity of reflective layer 121. In accordance with anotherembodiment of the present invention, when a very thin flash over-coat124 is placed over the highly reflecting layer, then the reflectivelayer 121 may be silver metal or a silver alloy because the flash layerprotects the reflective layer while still allowing the highly reflectinglayer 121 to contribute to the reflectivity of the mirror. In suchcases, a thin (between about 25 Å and about 300 Å) layer of rhodium,platinum, or molybdenum is deposited over the reflective layer 121. Whenreflective layer 121 is silver, flash layer 122 may also be a silveralloy.

It is preferred but not essential that the third surfacereflector/electrode 120 be maintained as the cathode in the circuitrybecause this eliminates the possibility of anodic dissolution or anodiccorrosion that might occur if the reflector/electrode was used as theanode. Although as can be seen in Table 1, if certain silver alloys areused, the positive potential limit of stability extends out far enough,e.g., 1.2 V, that the silver alloy reflector/electrode could safely beused as the anode in contact with at least one solution-phaseelectrochromic material.

TABLE 1 White Light Reflectance Negative Potential Limit PositivePotential Limit Reflectance In Device Contact of Window of PotentialWindow of Potential Metal In Air (%) Stability Stability (V) Stability(V) Al >92 N/A very poor N/A N/A Cr 65 N/A poor N/A N/A Stainless 60 N/Agood N/A N/A Steel Rh 75 N/A very good N/A N/A Pt 72 N/A very good N/AN/A Inconel 55 N/A N/A N/A N/A Ag 97 84 fair −2.29 0.86 Ag2.7Pd 93 81good −2.26 0.87 Ag10Pd 80 68 good −2.05 0.97 Ag6Pt 92 80 good −1.66*0.91 Ag6Au 96 84 good −2.25 0.98 Ag25Au 94 82 good −2.3 1.2 *This numberis suspect because the test was run in propylene carbonate containingsome water.

The various layers of reflector/electrode 120 can be deposited by avariety of deposition procedures, such as RF and DC sputtering, e-beamevaporation, chemical vapor deposition, electrodeposition, etc., thatwill be known to those skilled in the art. The preferred alloys arepreferably deposited by sputtering (RF or DC) a target of the desiredalloy or by sputtering separate targets of the individual metals thatmake up the desired alloy, such that the metals mix during thedeposition process and the desired alloy is produced when the mixedmetals deposit and solidify on the substrate surface.

In another embodiment, the reflector/electrode 120 shown in FIG. 4 hasat least two layers (121 and 122), where at least one layer of a basematerial 122 covers substantially the entire portion of the thirdsurface 114 a and at least one layer of a reflective material 121 coversthe inner section of the third surface 114 a, but does not cover theperipheral edge portion 125 where seal member 116 is disposed.Peripheral portion 125 may be created by masking that portion of layer122 during deposition of the layer of reflective material 121, or thelayer of reflective material may be deposited over the entire thirdsurface and subsequently removed or partially removed in the peripheralportion. The masking of layer 122 may be accomplished by use of aphysical mask or through other well-known techniques, such asphotolithography and the like. Alternatively, layer 122 may be partiallyremoved in the peripheral portion by a variety of techniques, such as,for example, by etching (laser, chemical, or otherwise), mechanicalscraping, sandblasting, or otherwise. Laser etching is the presentlypreferred method because of its accuracy, speed, and control. Partialremoval is preferably accomplished by laser etching in a pattern whereenough metal is removed to allow the seal member 116 to bond directly tothe third surface 114 a while leaving enough metal in this area suchthat the conductance in this area is not significantly reduced.

In addition, an optional intermediate layer of a conductive material 123may be placed over the entire area of third surface 114 a and disposedbetween the reflective layer 121 and the base layer 122, or it may beplaced only under the area covered by layer 121, i.e., not in peripheraledge portion 125. If this optional intermediate layer is utilized, itcan cover the entire area of third surface 114 a or it may be masked orremoved from the peripheral edge portion as discussed above.

An optional flash over-coat layer 124 may be coated over the reflectivelayer 121. The reflective layer 121, the optional intermediate layer123, and the base layer 122 preferably have properties similar to thatdescribed above, except that the layer of reflective material 121 neednot bond well to the epoxy seal, since it is removed in the peripheralportion where the seal member 116 is placed. Because the interactionwith the epoxy seal is removed, silver metal itself, in addition to thealloys of silver described above, will function as the reflective layer.Alternatively, an adhesion promoter can be added to the sealing materialwhich enhances adhesion to silver or silver alloys and the reflectivelayer can be deposited over most of the third surface includingsubstantial portions under the seal area. Such adhesion promoters aredisclosed in U.S. Pat. No. 6,157,480, entitled “IMPROVED SEAL FORELECTROCHROMIC DEVICES,” the disclosure of which is incorporated hereinby reference.

Referring again to FIG. 3, chamber 125, defined by transparent conductor128 (disposed on front element rear surface 112 b), reflector/electrode120 (disposed on rear element front surface 114 a), and an innercircumferential wall 132 of sealing member 116, contains anelectrochromic medium 126. Electrochromic medium 126 is capable ofattenuating light traveling therethrough and has at least onesolution-phase electrochromic material in intimate contact withreflector/electrode 120 and at least one additional electroactivematerial that may be solution-phase, surface-confined, or one thatplates out onto a surface. However, the presently preferred media aresolution-phase redox electrochromics, such as those disclosed inabove-referenced U.S. Pat. Nos. 4,902,108, 5,128,799, 5,278,693,5,280,380, 5,282,077, 5,294,376, and 5,336,448. U.S. Pat. No. 6,020,987,entitled “AN IMPROVED ELECTROCHROMIC MEDIUM CAPABLE OF PRODUCING APRE-SELECTED COLOR,” discloses electrochromic media that are perceivedto be gray throughout their normal range of operation. The entiredisclosure of this patent is hereby incorporated herein by reference. Ifa solution-phase electrochromic medium is utilized, it may be insertedinto chamber 125 through a sealable fill port 142 through well-knowntechniques, such as vacuum backfilling and the like.

A resistive heater 138, disposed on the fourth glass surface 114 b, mayoptionally be a layer of ITO, fluorine-doped tin oxide, or may be otherheater layers or structures well known in the art. Electricallyconductive spring clips 134 a and 134 b are placed on the coated glasssheets (112 and 114) to make electrical contact with the exposed areasof the transparent conductive coating 128 (clip 134 b) and the thirdsurface reflector/electrode 120 (clip 134 a). Suitable electricalconductors (not shown) may be soldered or otherwise connected to thespring clips (134 a and 134 b) so that a desired voltage may be appliedto the device from a suitable power source.

An electrical circuit 150, such as those taught in the above-referencedCanadian Patent No. 1,300945 and U.S. Pat. Nos. 5,204,778, 5,434,407,and 5,451,822, is connected to and allows control of the potential to beapplied across reflector/electrode 120 and transparent electrode 128,such that electrochromic medium 126 will darken and thereby attenuatevarious amounts of light traveling therethrough and thus vary thereflectance of the mirror containing electrochromic medium 126.

As stated above, the low resistance of reflector/electrode 120 allowsgreater design flexibility by allowing the electrical contact for thethird surface reflector/electrode to be small while maintaining adequatecoloring speed. This flexibility extends to improving theinterconnection techniques to the layer of transparent conductivematerial 128 on the second surface 112 b. Referring now to FIGS. 5 a and5 b, an improved mechanism for applying a drive potential to the layerof transparent conductive material 128 is shown. Electrical connectionbetween the power supply and the layer of transparent conductivematerial 128 is made by connecting the buss bars (or clips 119 a) to thearea of reflector/electrode 120 a, such that the drive potential travelsthrough the area of reflector/electrode 120 a and conductive particles116 b in sealing member 116 before reaching the transparent conductor128. The reflector/electrode must not be present in area 120 c, so thatthere is no chance of current flow from reflector/electrode area 120 ato 120 b. This configuration is advantageous in that it allowsconnection to the transparent conductive material 128 nearly all the wayaround the circumference, and therefore improves the speed of dimmingand clearing of the electrochromic media 126.

In such a configuration, sealing member 116 comprises a typical sealingmaterial, e.g., epoxy 116 a, with conductive particles 116 b containedtherein. The conductive particles may be small, such as, for example,gold, silver, copper, etc., coated plastic with a diameter ranging fromabout 5 microns to about 80 microns, in which case there must be asufficient number of particles to ensure sufficient conductivity betweenthe reflector/electrode area 120 a and the transparent conductivematerial 128. Alternatively, the conductive particles may be largeenough to act as spacers, such as, for example, gold, silver, copper,etc., coated glass or plastic beads. The reflector/electrode 120 isseparated into two distinct reflector/electrode areas (120 a and 120 b,separated by an area 120 c devoid of reflector/electrode). There aremany methods of removing the reflector/electrode 120 from area 120 c,such as, for example, chemical etching, laser ablating, physical removalby scraping, etc. Deposition in area 120 c can also be avoided by use ofa mask during deposition of reflector/electrode. Sealing member 116 withparticles 116 b contacts area 120 a such that there is a conductive pathbetween reflector/electrode area 120 a and the layer of transparentconductive material 128. Thus, electrical connection to thereflector/electrode area 120 b that imparts a potential to theelectrochromic medium is connected through clips 119 b to the electroniccircuitry at reflector/electrode area 120 d (FIG. 5 b). No conductiveparticles 116 b can be placed in this reflector/electrode area 120 bbecause of the possibility of an electrical short betweenreflector/electrode area 120 b and the layer of transparent conductivematerial 128. If such an electrical short occurred, the electrochromicdevice would not operate properly. Additionally, no conductive seal 116b should be present in area 120 b.

A variety of methods can be used to ensure that no conductive particles116 b enter into this reflector/electrode area 120 b, such as, forexample, disposing a nonconductive material into the area 120 c ofreflector/electrode devoid of conductive material. A dual dispensercould be used to deposit the seal 116 with conductive particles 116 bonto reflector/electrode area 120 a and simultaneously deposit thenonconductive material into reflector/electrode area 120 c. Anothermethod would be to cure a nonconductive seal in area 120 c and thendispose a conductive material 116 c into the edge gap to electricallyinterconnect reflector/electrode area 120 a with transparent conductivelayer 128. A general method of ensuring that no conductive particlesreach reflector/electrode area 120 b is to make sure seal 116 has properflow characteristics, such that the conductive portion 116 b tends tostay behind as the sealant is squeezed out during assembly, and only thenon-conductive portion of 116 flows into area 120 b. In an alternativeembodiment, spacer member 116 need not contain conductive particles anda conductive member or material 116 c may be placed on or in the outeredge of member 116 to interconnect transparent conductive material 128to reflector/electrode area 120 a.

Yet another embodiment of an improved electrical interconnectiontechnique is illustrated in FIG. 6, where a first portion of seal member116 is applied directly onto the third surface 114 a and cured prior tothe application of reflector/electrode 120. After thereflector/electrode 120 is deposited onto the third surface 114 a overthe first portion of seal member 116, a portion of the cured seal member116 is machined off to leave 116 i as shown with a predeterminedthickness (which will vary depending on the desired cell spacing betweenthe second surface 112 b and the third surface 114 a). The cell spacingranges from about 20 microns to about 1500 microns, and preferablyranges from about 90 microns to about 750 microns. By curing the firstportion of seal member and machining it to a predetermined thickness(116 i), the need for glass beads to ensure a constant cell spacing iseliminated. Glass beads are useful to provide cell spacing, however,they provide stress points where they contact reflector/electrode 120and transparent conductor 128. By removing the glass beads, these stresspoints are also removed. During the machining, the reflector/electrode120 that is coated on first portion of seal member 116 is removed toleave an area devoid of reflector/electrode 120. A second portion ofseal member 116 ii is then deposited onto the machined area of the firstportion of seal member 116 i or on the coatings on second surface 112 bin the area corresponding to 116 i, and seal member 116 ii is curedafter assembly in a conventional manner. Finally, an outer conductiveseal member 117 may optionally be deposited on the outer peripheralportion of seal member 116 to make electrical contact between the outeredge of reflector/electrode 120 and the outer peripheral edge of thelayer of transparent conductive material 128. This configuration isadvantageous in that it allows connection to the transparent conductivematerial 128 nearly all the way around the circumference, and thereforeimproves the speed of dimming and clearing of the electrochromic media126.

Referring again to FIG. 2, rearview mirrors embodying the presentinvention preferably include a bezel 144, which extends around theentire periphery of each individual assembly 110, 111 a, and/or 111 b.The bezel 144 conceals and protects the spring clips 134 a and 134 b ofFIG. 3 (or 116 a and 116 b of FIG. 5 a; 116 i, 116 ii, and 117 of FIG.6), and the peripheral edge portions of the sealing member and both thefront and rear glass elements (112 and 114, respectively). A widevariety of bezel designs are well known in the art, such as, forexample, the bezel taught and claimed in above-referenced U.S. Pat. No.5,448,397. There are also a wide variety of housings well known in theart for attaching the mirror assembly 110 to the inside front windshieldof an automobile, or for attaching the mirror assemblies 111 a and 111 bto the outside of an automobile. A preferred mounting bracket isdisclosed in above-referenced U.S. Pat. No. 5,337,948.

The electrical circuit preferably incorporates an ambient light sensor(not shown) and a glare light sensor 160, the glare light sensor beingpositioned either behind the mirror glass and looking through a sectionof the mirror with the reflective material completely or partiallyremoved, or the glare light sensor can be positioned outside thereflective surfaces, e.g., in the bezel 144 or as described below, thesensor can be positioned behind a uniformly deposited transflectivecoating. Additionally, an area or areas of the electrode and reflector,such as 146, may be completely removed or partially removed as describedbelow to permit a vacuum fluorescent display, such as a compass, clock,or other indicia, to show through to the driver of the vehicle or asalso described below, this light emitting display assembly can be shownthrough a uniformly deposited transflective coating. The presentinvention is also applicable to a mirror which uses only one video chiplight sensor to measure both glare and ambient light and which isfurther capable of determining the direction of glare. An automaticmirror on the inside of a vehicle, constructed according to thisinvention, can also control one or both outside mirrors as slaves in anautomatic mirror system.

The following illustrative examples are not intended to limit the scopeof the present invention but to illustrate its application and use:

EXAMPLE 1

Electrochromic mirror devices incorporating a high reflectivity thirdsurface reflector/electrode were prepared by sequentially depositingapproximately 700 Å of chromium and approximately 500 Å of silver on thesurface of 2.3-mm thick sheets of flat soda lime float glass cut to anautomotive mirror element shape. A second set of high reflectivity thirdsurface reflector/electrodes were also prepared by sequentiallydepositing 700 Å of chromium and approximately 500 Å of a silver alloycontaining 3 percent by weight palladium on the glass element shapes.The deposition was accomplished by passing the said glass element shapespast separate metal targets in a magnetron sputtering system with a basepressure of 3×10⁻⁶ torr and an argon pressure of 3×10⁻³ torr.

The chromium/silver and chromium/silver 3 percent palladium alloy coatedglass automotive mirror shapes were used as the rear planar elements ofan electrochromic mirror device. The front element was a sheet of TEC 15transparent conductor coated glass from LOF cut similar in shape andsize to the rear glass element. The front and rear elements were bondedtogether by an epoxy perimeter seal, with the conductive planar surfacesfacing each other and parallel to each other with an offset. The spacingbetween the electrodes was about 137 microns. The devices were vacuumfilled through a fill port left in the perimeter seal with anelectrochromic solution made up of:

-   -   0.028 molar 5,10-dihydro-5-10-dimethylphenazine    -   0.034 molar 1,1′-di(3-phenyl(n-propane))-4,4′-bipyridinium        di(tetrafluoroborate)    -   0.030 molar 2-(2′-hydroxy-5′-methylphenyl)-benzotriazole        in a solution of 3 weight percent Elvacite™ 2051        polymethylmethacrylate resin dissolved in propylene carbonate.

The fill port was plugged with an UV cure adhesive, which was cured byexposure to UV light.

The devices were subjected to accelerated durability tests until theseal integrity of the device was breached or the lamination of thereflector/electrode layers or the transparent electrode layers weresubstantially degraded or dilapidated, at which time the device is saidto fail. The first test performed was steam autoclave testing in whichthe devices were sealed in a water-containing vessel and subjected to120° C. at a pressure of 15 pounds per square inch (psi). The secondtest performed was copper-accelerated acetic acid-salt spray (CASS) asdescribed in ASTM B 368-85.

When the electrochromic devices were observed after one day in testing,all of the devices failed to withstand the CASS testing, and all of thedevices failed to withstand the steam autoclave testing.

EXAMPLE 2

Other than as specifically mentioned, the devices in this example wereconstructed in accordance with the conditions and teachings inExample 1. Multilayer combination reflector/electrodes were prepared bysequentially depositing approximately 700 Å chromium, approximately 100Å rhodium, and approximately 500 Å of silver on the surface of the glasselement shapes. A second set of multilayer combinationreflector/electrodes were also prepared by sequentially depositingapproximately 700 Å of chromium, approximately 100 Å rhodium, andapproximately 500 Å of a silver alloy containing 3 percent by weightpalladium on the surface of said glass element shapes. Theelectrochromic devices were constructed and tested in accordance withExample 1.

The device incorporating the sequential multilayer combination reflectorelectrode of chromium, rhodium, and silver withstood steam autoclavetesting two times longer and CASS testing 10 times longer than thedevice in Example 1 before failure occurred. The device incorporatingthe sequential multilayer combination reflector electrode of chromium,rhodium, and silver 3 percent palladium alloy withstood steam autoclavetesting three times longer and CASS testing 10 times longer than devicesin Example 1 before failure occurred.

EXAMPLE 3

Other than as specifically mentioned, the devices in this example wereconstructed in accordance with the conditions and teachings inExample 1. Multilayer combination reflector/electrodes were prepared bysequentially depositing approximately 700 Å chromium, approximately 500Å molybdenum and approximately 500 Å of a silver alloy containing 3percent by weight palladium on the surface of said glass element shapes.The electrochromic devices were constructed and tested in accordancewith Example 1.

The device incorporating the sequential multilayer combination reflectorelectrode of chromium, molybdenum, and silver 3 percent palladium alloywithstood CASS testing 10 times longer than devices in Example 1 beforefailure occurred.

EXAMPLE 4

Other than as specifically mentioned, the devices in this example wereconstructed in accordance with the conditions and teachings inExample 1. Multilayer combination reflector/electrodes were prepared bysequentially depositing approximately 700 Å chromium, approximately 500Å of a silver alloy containing 3 percent by weight palladium, andapproximately 100 Å of molybdenum on the surface of said glass elementshapes. A second set of multilayer combination reflector/electrodes werealso prepared by sequentially depositing approximately 700 Å ofchromium, approximately 500 Å molybdenum, approximately 500 Å of asilver alloy containing 3 percent by weight palladium, and approximately100 Å of molybdenum on the surface of said glass element shapes. Theelectrochromic devices were constructed and tested in accordance withExample 1.

The device incorporating the sequential multilayer combination reflectorelectrode of chromium, molybdenum, silver 3 percent palladium, andmolybdenum withstood steam autoclave testing 25 percent longer and CASStesting twelve times longer than the sequential multilayer combinationreflector electrode device of chromium, silver 3 percent palladium,molybdenum before failure occurred. Also, the device incorporating thesequential multilayer combination reflector electrode of chromium,molybdenum, silver 3 percent palladium, molybdenum withstood CASStesting three times longer than the device constructed in Example 3.Finally, the sequential multilayer combination reflector electrodedevice of chromium, silver 3 percent palladium, molybdenum withstood twotimes longer in CASS testing and twenty times longer in steam autoclavetesting than the sequential multilayer combination reflector electrodedevice of chromium, silver 3 percent palladium of Example 1.

EXAMPLE 5

Other than as specifically mentioned, the devices in this example wereconstructed in accordance with the conditions and teachings inExample 1. Multilayer combination reflector/electrodes were prepared bysequentially depositing approximately 700 Å chromium, approximately 100Å rhodium and approximately 500 Å of silver on the surface of said glasselement shapes. A second set of multilayer combinationreflector/electrodes were also prepared by sequentially depositingapproximately 700 Å of chromium, approximately 100 Å rhodium, andapproximately 500 Å of a silver alloy containing 3 percent by weightpalladium on the surface of said glass element shapes. A third set ofmultilayer combination reflector/electrodes was also prepared bysequentially depositing approximately 700 Å of chromium, approximately100 Å rhodium, and approximately 500 Å of a silver alloy containing 6percent by weight platinum on the surface of said glass element shapes.A fourth set of multilayer combination reflector/electrodes was alsoprepared by sequentially depositing approximately 700 Å of chromium,approximately 100 Å rhodium, and approximately 500 Å of a silver alloycontaining 6 percent by weight gold on the surface of said glass elementshapes. A fifth set of multilayer combination reflector/electrodes wasalso prepared by sequentially depositing approximately 700 Å ofchromium, approximately 100 Å rhodium, and approximately 500 Å of asilver alloy containing 25 percent by weight gold on the surface of saidglass element shapes. The electrochromic devices were constructed inaccordance with Example 1.

Conductive clips were connected to the offset portions of the front andrear elements of the devices. A power source was connected to the clipsand 1.2 volts was applied to the devices continuously for approximately250 hours at approximately 20° C., with the connection arranged suchthat the reflector/electrode was the cathode. The device incorporatingthe sequential multilayer combination reflector electrode of chromium,rhodium, and silver exhibited a yellowing effect within theelectrochromic medium. This yellowing phenomenon was not apparent in anyof the silver alloy devices.

FIGS. 7A-7G illustrate various alternative constructions for anelectrochromic rearview mirror of the present invention, particularlywhen a light source 170, such as an information display (i.e.,compass/temperature display) or signal light, is positioned within themirror assembly behind the electrochromic mirror. According to the firstconstruction shown in FIG. 7A, the electrochromic rearview mirror wasconstructed similar to those described above, with the exception thatsecond electrode 120 includes a window 146 in the layer 121 ofreflective material in a region of second electrode 120 that is in frontof light source 170. Electrode 120 further includes a coating 172 ofelectrically conductive material that is applied over substantially allof the front surface 114 a of rear element 114. Coating 172 ispreferably at least partially transmissive so as to enable light emittedfrom light source 170 to be transmitted through the electrochromicmirror via window 146. By providing electrically conductive coating 172throughout the entire area of window 146, the electrochromic media 125in the region of window 146 will respond to the voltage applied to theclips as though window 146 was not even present. Coating 172 may be asingle layer of a transparent conductive material. Such a single layermay be made of the same materials as that of first electrode 128 (i.e.,indium tin oxide, etc.).

Transparent electrodes made of ITO or other transparent conductors havebeen optimized at thicknesses to maximize the transmission of visiblelight (typically centered around 550 nm). These transmission optimizedthicknesses are either very thin layers (<300 Å) or layers optimized atwhat is commonly called ½ wave, full wave, 1½ wave, etc. thickness. ForITO, the ½ wave thickness is about 1400 Å and the full wave thickness isaround 2800 Å. Surprisingly, these thicknesses are not optimum fortransflective (i.e., partially transmissive, partially reflective)electrodes with a single underlayer of a transparent conductor under ametal reflector such as silver or silver alloys. The optimum thicknessesto achieve relative color neutrality of reflected light are centeredaround ¼ wave, ¾ wave, ¼ wave, etc. optical thicknesses for light of 500nm wavelength. In other words the optimal optical thickness for such alayer when underlying a metal reflector such as silver or silver alloyis mλ/4, where λ is the wavelength of light at which the layer isoptimized (e.g., 500 nm) and m is an odd integer. These optimumthicknesses are ¼ wave different from the transmission optima for thesame wavelength. Such a single layer may have a thickness of between 100Å and 3500 Å and more preferably between 200 Å and 250 Å, and a sheetresistivity of between about 3Ω/Y and 300Ω/Y and preferably less thanabout 100Ω/Y.

Layer 121 may be made of any of the reflective materials described aboveand is preferably made of silver or a silver alloy. The thickness ofreflective layer 121 in the arrangement shown in FIG. 7A is preferablybetween 30 Å and 800 Å. The thickness of layer 121 will depend on thedesired reflectance and transmittance properties. For an inside rearviewmirror, layer 121 preferably has a reflectance of at least 60 percentand a transmittance through window 146 of 10 to 50 percent. For anoutside mirror, the reflectance is preferably above 35 percent and thetransmittance is preferably approximately 10 to 50 percent and morepreferably at least 20 percent for those regions that are in front ofone of the lights of a signal light (as described in more detail below).

Window 146 in layer 121 may be formed by masking window area 146 duringthe application of the reflective material. At this same time, theperipheral region of the third surface may also be masked so as toprevent materials such as silver or silver alloy (when used as thereflective material) from being deposited in areas to which seal 116must adhere, so as to create a stronger bond between seal 116 andcoating 172. Additionally, an area in front of sensor 160 (FIG. 2) mayalso be masked. Alternatively, an adhesion promoting material can beadded to the seal to enhance adhesion between the seal and thesilver/silver alloy layer as described in the above-referenced U.S. Pat.No. 6,157,480.

An alternative construction to that shown in FIG. 7A is shown in FIG.7B, where electrically conductive coating 172 is formed of a pluralityof layers 174 and 176. For example, coating 172 may include a first baselayer 174 applied directly to front surface 114 a of rear element 114,and an intermediate second layer 176 disposed on first layer 174. Firstlayer 174 and second layer 176 are preferably made of materials thathave relatively low sheet resistivity and that are at least partiallytransmissive. The materials forming layers 174 and 176 may also bepartially reflective. If the light emitting display behind the partiallytransmissive window area 146 must be viewed often in bright ambientconditions or direct sunlight, it may be desirable to keep thereflectivity of the window area to a minimum by using metals with lowreflectivity or other dark, black or transparent coatings that areelectrically conductive.

The material forming layer 174 should exhibit adequate bondingcharacteristics to glass or other materials of which rear element 114may be formed, while the material forming layer 176 should exhibitadequate properties so as to bond to the material of layer 174 andprovide a good bond between the applied layer 121 and seal 116. Thus,the material used for layer 174 is preferably a material selected fromthe group consisting essentially of: chromium,chromium-molybdenum-nickel alloys, nickel-iron-chromium alloys, silicon,tantalum, stainless steel, and titanium. In the most preferredembodiment, layer 174 is made of chromium. The material used to formsecond layer 176 is preferably a material selected from the groupconsisting essentially of, but not limited to: molybdenum, rhodium,nickel, tungsten, tantalum, stainless steel, gold, titanium, and alloysthereof. In the most preferred embodiment, second layer 176 is formed ofnickel, rhodium, or molybdenum. If first layer 174 is formed ofchromium, layer 174 preferably has a thickness of between 5 Å and 50 Å.If the layer of chromium is much thicker, it will not exhibit sufficienttransmittance to allow light from a light source 170, such as a displayor signal light, to be transmitted through window 146. The thickness oflayer 176 is selected based upon the material used so as to allowbetween 10 to 50 percent light transmittance through both of layers 174and 176. Thus, for a second layer 176 formed of either rhodium, nickel,or molybdenum, layer 176 is preferably between 50 Å and 150 Å. While thethicknesses of layers 174 and 176 are preferably selected to be thinenough to provide adequate transmittance, they must also be thick enoughto provide for adequate electrical conductivity so as to sufficientlyclear or darken electrochromic media 125 in the region of window 146.The coating 172 should thus have a sheet resistivity of less than 100Ω/Yand preferably less than 50Ω/Y to 60Ω/Y.

The arrangement shown in FIG. 7B provides several advantages over theconstruction shown and described with respect to FIG. 7A. Specifically,the metals used in forming coating 172 contribute to the totalreflectance of reflector electrode 120. Accordingly, the layer of thereflective material 121 need not be made as thick. If, for example,silver or a silver alloy is used to form layer 121, the layer ofthickness is between 50 Å and 150 Å, thereby eliminating some of thematerial costs in providing the reflective layer. Further, the use ofreflective metals in forming coating 172 provides for a degree ofreflectance within window 146, thereby providing a much more asceticallypleasing appearance than if window 146 were devoid of any reflectivematerial whatsoever. Ideally, coating 172 provides between 30 and 40percent reflectivity in window 146. If the reflectance in window 146 istoo high, bright light will tend to wash out the display in the sensethat it eliminates the contrast between the light of the display andlight reflecting outward from coating 172.

Another benefit of utilizing metals to form conductive coating 172 isthat such metals are much easier and less expensive to process thanmetal oxides, such as indium tin oxide. Such metal oxides requireapplication in oxygen-rich chambers at very high temperatures, whereasmetal layers may be deposited without special oxygen chambers and atmuch lower temperatures. Thus, the process for applying multiple metallayers consumes much less energy and is much less expensive than theprocesses for forming metal oxide layers.

A third alternate arrangement for the electrochromic mirror of thepresent invention is shown in FIG. 7C. The construction shown in FIG. 7Cis essentially the same as that shown in FIG. 7B except that a thinsilver or silver alloy layer 178 is formed on conductive coating 172within window 146. By providing only a thin layer 178 of reflectivematerial in window 146, adequate transmittance may still be providedthrough window 146 while increasing the reflectivity and electricalconductivity in that area. Layer 178 may have a thickness of between 40Å and 150 Å, whereas the layer of reflective material 121 in the otherareas may have a thickness in the order of between 200 Å and 1000 Å. Thethin layer 178 of reflective material may be formed by initially maskingthe area of window 178 while applying a portion of reflective layer 121and then removing the mask during deposition of the remainder of layer121. Conversely, a thin layer of reflective material may first bedeposited and then a mask may be applied over window 146 while theremainder of reflective layer 121 is deposited. As will be apparent tothose skilled in the art, thin layer 178 may also be formed withoutmasking by depositing reflective layer 121 to its full thickness andsubsequently removing a portion of layer 121 in the region of window146.

A modification of the configuration shown in FIG. 7C is illustrated inFIG. 7D. As will be apparent from a comparison of the drawings, theconstruction of FIG. 7D only differs from that shown in FIG. 7C in thatlayers 174 and 176 constituting conductive coating 172 are made thinner(designated as thin layers 180 and 181) in the region ofreflector/electrode 120 that is in front of light source 170. As such,thin layer 180 may have a thickness of between 5 Å and 50 Å, whereaslayer 174 may have thicknesses anywhere between 100 Å and 1000 Å.Similarly, thin layer 181 may be made of the same material as layer 176but would have a thickness of between 50 Å and 150 Å, while layer 176may have thicknesses on the order of 100 Å to 1000 Å. Thus, with theconstruction shown in FIG. 7D, the electrical conductivity,reflectivity, and transmittance within region 146 may be optimizedwithin that region while enabling the reflectance and electricalconductivity in the other regions to be optimized without concern as tothe transmittance in those areas.

FIG. 7E shows yet another alternative construction for second electrode120. In the construction shown in FIG. 7E, second electrode 120 includesan electrically conductive coating 172 and a reflective coating 178formed over the entire third surface 114 a of the mirror. By makingreflective coating 178 uniformly partially transmissive, a light source,such as a display or signal light, may be mounted in any location behindthe mirror and is not limited to positioning behind any particularwindow formed in second electrode 120. Again, for a rearview mirror,second electrode 120 preferably has a reflectance of at least 35 percentfor an outside mirror and at least 60 percent for an inside mirror and atransmittance of preferably at least 10 percent. Conductive coating 172is preferably a single layer of ITO or other transparent conductivematerials, but may also consist of one or more layers of the partiallyreflective/partially transmissive electrically conductive materialsdiscussed above.

Reflective coating 178 may be constructed using a single, relativelythin, layer of a reflective electrically conductive material such assilver, silver alloy, or the other reflective materials discussed above.If the reflective material is silver or a silver alloy, the thickness ofsuch a thin layer should be limited to about 500 Å or less, and atransparent conductive material, such as ITO or the like, should beutilized as electrically conductive layer 172, such that secondelectrode 120 may have sufficient transmittance to allow a display orsignal light to be viewed from behind the mirror. On the other hand, thethickness of the single layer of reflective material should be about 10Å or more depending upon the material used to ensure sufficientreflectivity.

To illustrate the features and advantages of an electrochromic mirrorconstructed in accordance with the embodiment shown in FIG. 7E, tenexamples are provided below. In these examples, references are made tothe spectral properties of models of electrochromic mirrors constructedin accordance with the parameters specified in each example. Indiscussing colors, it is useful to refer to the CommissionInternationale de I′Eclairage's (CIE) 1976 CIELAB Chromaticity Diagram(commonly referred to as the L*a*b* chart). The technology of color isrelatively complex, but a fairly comprehensive discussion is given by F.W. Billmeyer and M. Saltzman in Principles of Color Technology, 2ndEdition, J. Wiley and Sons Inc. (1981), and the present disclosure, asit relates to color technology and terminology, generally follows thatdiscussion. On the L*a*b* chart, L* defines lightness, a* denotes thered/green value, and b* denotes the yellow/blue value. Each of theelectrochromic media has an absorption spectra at each particularvoltage that may be converted to a three number designation, theirL*a*b* values. To calculate a set of color coordinates, such as L*a*b*values, from the spectral transmission or reflectance, two additionalitems are required. One is the spectral power distribution of the sourceor illuminant. The present disclosure uses CIE Standard Illuminant A tosimulate light from automobile headlamps and uses CIE StandardIlluminant D₆₅ to simulate daylight. The second item needed is thespectral response of the observer. The present disclosure uses the 2degree CIE standard observer. The illuminant/observer combinationgenerally used for mirrors is then represented as A/2 degree and thecombination generally used for windows is represented as D₆₅/2 degree.Many of the examples below refer to a value Y from the 1931 CIE Standardsince it corresponds more closely to the spectral reflectance than L*.The value C*, which is also described below, is equal to the square rootof (a*)²+(b*)², and hence, provides a measure for quantifying colorneutrality.

It should be noted that the optical constants of materials vary somewhatwith deposition method and conditions employed. These differences canhave a substantial effect on the actual optical values and optimumthicknesses used to attain a value for a given coating stock.

According to a first example, an electrochromic mirror was modeledhaving a back plate 114 (FIG. 7E) of glass, a layer 172 of ITO ofapproximately 2000 Å, a layer 178 of an alloy of silver containing 6percent gold (hereinafter referred to as 6Au94Ag) of approximately 350Å, an electrochromic fluid/gel layer 125 having a thickness ofapproximately 140 microns, a layer 128 of approximately 1400 Å of ITO,and a glass plate 112 of 2.1 mm. Using D65 illuminant at 20 degree angleof incidence, the model outputs were Y=70.7, a*=+1, and b*=+9.5. Thismodel also indicated a spectrally dependent transmittance that was 15percent over the blue-green region decreasing in the red color region ofthe spectrum to approximately 17 percent in the blue-green region of thespectrum. Elements were constructed using the values and the model astarget parameters for thickness, and the actual color, and reflectionvalues corresponded closely to those models with transmission values ofapproximately 15 percent in the blue and green region. In this example,1400 Å ITO (½ wave) would produce a far more yellow element (b* ofapproximately 18).

Typically, thin silver or silver alloy layers are higher in blue-greentransmission and lower in blue-green light reflection which imparts ayellow hue to the reflected image. The 2000 Å ITO underlayer ofapproximately ¾ wave in thickness supplements the reflection ofblue-green light which results in a more neutral hue in reflection.Other odd quarter wave multiples (i.e., ¼, 5/4, 7/4, etc.) are alsoeffective in reducing reflected color hue. It should be noted that othertransparent coatings, such as (F)SnO or (AL)ZnO, or a combination ofdielectric, semi-conductive, or conductive coatings, can be used tosupplement blue-green reflection and produce a more neutral reflectedhue in the same manner.

According to a second example of the embodiment illustrated in FIG. 7E,an electrochromic mirror was modeled having a back plate 114 of glass,layer 172 including a sublayer of titanium dioxide of approximately 441Å and a sublayer of ITO of 200 Å, a layer 178 of 6Au94Ag ofapproximately 337 Å, an electrochromic fluid/gel 125 having a thicknessof approximately 140 microns, a layer 128 of approximately 1400 Å ofITO, and a glass plate 112 of 2.1 mm. In air, the model of theconductive thin film 120 on glass 114 for this example, using D65illuminant at 20 degree angle of incidence, exhibited values ofapproximately Y=82.3, a*=0.3, and b*=4.11. This model also indicated arelatively broad and uniform transmittance of 10-15 percent across mostof the visible spectrum, making it an advantageous design for aninterior rearview mirror with a multi-colored display or a white lightdisplay or illuminator. When this back plate system 114, 120 isincorporated into an electrochromic mirror, the predicted overallreflectance decreases and the transmittance increases.

According to a third example of an electrochromic mirror constructed asshown in FIG. 7E, an electrochromic mirror was modeled having a backplate 114 of glass, a layer 172 including a sublayer of titanium dioxideof approximately 407 Å and a sublayer of ITO of 200 Å, a layer 178 of6Au94Ag of approximately 237 Å, an electrochromic fluid/gel layer 125having a thickness of approximately 140 microns, a layer 128 ofapproximately 1400 Å of ITO, and a glass plate 112 of 2.1 mm. In air,the model of the conductive thin film 120 on glass 114, for thisexample, using D65 illuminant at 20 degree angle of incidence, exhibitedvalues of approximately Y=68.9, a*=0.03, and b*=1.9. This model alsoindicated a relatively broad and uniform transmittance of approximately25 to 28 percent across most of the visible spectrum, making it anadvantageous design for an exterior rearview mirror with a multi-colordisplay or a white light display or illuminator. When this back platesystem 114, 120 is incorporated into an electrochromic mirror, thepredicted overall reflectance decreases and the transmittance increases.

According to a fourth example of the embodiment shown in FIG. 7E, anelectrochromic mirror was modeled having a back plate 114 of glass, alayer 172 including a sublayer of titanium dioxide of approximately 450Å and a sublayer of ITO of 1600 Å, a layer 178 of 6Au94Ag ofapproximately 340 Å, an electrochromic fluid/gel layer 125 having athickness of approximately 140 microns, a layer 128 of approximately1400 Å of ITO, and a glass plate 112 of 2.1 mm. In air, the model of theconductive thin film 120 on glass 114, for this example, using D65illuminant at 20 degree angle of incidence, exhibited values ofapproximately Y=80.3, a*=−3.45, and b*=5.27. This model also indicated arelative transmittance peak at about 600 nm of approximately 17 percent.When this back plate system 114, 120 is incorporated into anelectrochromic mirror, the predicted overall reflectance decreases andthe transmittance increases. As one compares this stack to the secondexample, it illustrates, in part, a principle of repeating optima in theprimarily transmissive layer or layers (e.g., layer 172) of thesedesigns as one increases their thickness or thicknesses. The optima willbe determined by several factors which will include good colorneutrality, reflection, and transmission.

According to a fifth example of the embodiment shown in FIG. 7E, anelectrochromic mirror was modeled having a back plate 114 of glass; alayer 172 including a sublayer of titanium dioxide of approximately 450Å, a sublayer of ITO of 800 Å, a sublayer of silica of 50 Å, and anadditional sublayer of ITO of 800 Å; a layer 178 of 6Au94Ag ofapproximately 340 Å; an electrochromic fluid/gel layer 125 having athickness of approximately 140 microns, a layer 128 of approximately1400 Å of ITO; and a glass plate 112 of 2.1 mm. In air, the model of theconductive thin film 120 on glass 114, for this example, using D65illuminant at 20 degree angle of incidence, exhibited values ofapproximately Y=80.63, a*=−4.31, and b*=6.44. This model also indicateda relative transmittance peak at about 600 nm of approximately 17percent. When this back plate system is incorporated into anelectrochromic mirror, the predicted overall reflectance decreases andthe transmittance increases. This stack also demonstrates, in part, aprinciple of a flash layer incorporation in these designs. In thisparticular case, the 50 Å silica layer does not contribute substantiallyto the design when compared to the fourth example, nor does it detractfrom it greatly. The insertion of such layers would not, in the opinionof the inventors, circumvent any claims that might depend on the numberof layers or the relative refractive indices of layer sets. Flash layershave been shown to impart substantial advantages when used over layer178 and are discussed above. It is also believed that such flash layerscould have adhesion promotion or corrosion resistance advantages whenpositioned between layers 172 and 178 as well as between glass 114 andlayer(s) 120, especially when comprised of metal/alloys mentioned aboveas having such functions in thicker layers.

According to a sixth example of the embodiment shown in FIG. 7E, anelectrochromic mirror was modeled having a back plate 114 of glass, alayer 172 including a sublayer of titanium dioxide of approximately 450Å and a sublayer of ITO of 1600 Å, a layer 178 of silver of 290 Å and aflash layer of 6Au94Ag of approximately 50 Å, an electrochromicfluid/gel layer 125 having a thickness of approximately 140 microns, alayer 128 of approximately 1400 Å of ITO, and a glass plate 112 of 2.1mm. In air, on glass 114, the model of the conductive thin film 120 forthis example, using D65 illuminant at 20 degree angle of incidence,exhibited values of approximately Y=81.3, a*=−3.26, and b*=4.16. Thismodel also indicated a relative transmittance peak at about 600 nm ofabout 17 percent. When this back plate system 114, 120 is incorporatedinto an electrochromic mirror, the predicted overall reflectancedecreases and the transmittance increases. As one compares this stack tothe fourth example, it illustrates, in part, the principle of using aflash layer of a silver alloy over silver. The potential advantages ofsuch a system for layer 178, as opposed to a single alloy layer per thefourth example, include, but are not limited to, reduced cost, increasedreflectivity at the same transmission or increased transmissivity at thesame reflectance, decreased sheet resistance, and the possibility ofusing a higher percentage of alloyed material in the flash overcoatlayer to maintain enhanced electrode surface properties the silver alloyexhibits over pure silver. Similar potential advantages apply to thecases of different percentage alloys or a graded percentage alloy inlayer 178.

According to a seventh example of the embodiment shown in FIG. 7E, anelectrochromic mirror was modeled having a back plate 114 of glass, alayer 172 of silicon of approximately 180 Å, a layer 178 of 6Au94Ag ofapproximately 410 Å, an electrochromic fluid/gel layer 125 having athickness of approximately 140 microns, a layer 128 of approximately1400 Å of ITO, a glass plate 112 of 2.1 mm. In air, on glass 114, themodel of the conductive thin film 120 for this example, using D65illuminant at 20 degree angle of incidence, exhibited values of Y=80.4,a*=0.9, and b*=−3.39. In contrast, a thin layer of 6Au94Ag on glass withsimilar reflectivity exhibits a yellow hue in reflection. The model alsoindicated a spectrally dependent transmittance that reached a peak ofabout 18 percent at 580 nm. When this back plate system 114, 120 isincorporated into an electrochromic mirror, the predicted overallreflectance and the transmittance increases. In this case, the valueswould be appropriate for an automotive interior transflective mirror.This system would be especially useful if the silicon were deposited asa semi-conductive material, thereby allowing for masking of the silveralloy layer so that the silver alloy would be deposited primarily in theviewing area while still maintaining conductivity to the area to bedarkened.

According to an eighth example of the embodiment shown in FIG. 7E, anelectrochromic rearview mirror was modeled having a back plate 114 ofglass, a layer 172 including a sublayer of silicon of approximately 111Å and a sublayer of ITO of approximately 200 Å, a layer 178 of 6Au94Agof approximately 340 Å, an electrochromic fluid/gel layer 125 having athickness of approximately 140 microns, a layer 128 of approximately1400 Å of ITO, and a glass plate 112 of 2.1 mm. In air, on glass 114,the model of the conductive thin film 120 for this example using D65illuminant at 20 degree angle of incidence exhibited values ofapproximately Y=80.7, a*=0.1, and b*=−1.7. The model also indicated aspectrally dependent transmittance that reached a peak at about 18percent at 600 nm. When this back plate system 114, 120 is incorporatedinto an electrochromic mirror, the predicted overall reflectancedecreases and the transmittance increases. In this case, the valueswould be appropriate for an automotive transflective mirror. Also inthis case, masking of the silver alloy layer could take place in theseal area, and the conductivity of the back electrode of the systemwould be maintained by the ITO layer whether or not the silicon weresemi-conductive. This example is advantageous in that it utilizes thinlayers, which are easier to form during high volume manufacturing.

According to a ninth example of the embodiment shown in FIG. 7E, anelectrochromic mirror was modeled having a back plate 114 of glass, alayer 172 including a sublayer of silicon of approximately 77 Å and asublayer of ITO of approximately 200 Å, a layer 178 of 6Au94Ag ofapproximately 181 Å, an electrochromic fluid/gel layer 125 having athickness of approximately 140 microns, a layer 128 of approximately1400 Å of ITO, and a glass plate 112 of 2.1 mm. In air, on glass, themodel of the conductive thin film 120 for this example, using D65illuminant at 20 degree angle of incidence, exhibited values ofapproximately Y=64.98, a*=1.73, and b*=−2.69. The model also indicated aspectrally dependent transmittance that reached a peak of about 35percent at 650 nm. When this back plate system is incorporated into anelectrochromic mirror, the predicted overall reflectance decreases andthe transmittance increases. In this case, the values would beappropriate for an automotive exterior transflective mirror.

According to a tenth example of the embodiment shown in FIG. 7E, anelectrochromic mirror was modeled having a back plate 114 of glass, alayer 172 of fluorine-doped tin oxide of approximately 1957 Å (¾ waveoptima thickness), a layer 178 of 6Au94Ag of approximately 350 Å, anelectrochromic fluid/gel layer 125 having a thickness of approximately140 microns, a layer 128 of approximately 1400 Å of ITO, and a glassplate 112 of 2.1 mm. In air, on glass 114, the model of the conductivethin film 120, for this example, using D65 illuminant at 20 degree angleof incidence, exhibited outputs of approximately Y=80.38, a*=1.04, andb*=5.6. The model also indicated a spectrally dependent transmittancethat overall diminished as wavelength increased in the visible range.Transmittance at 630 nm was predicted as approximately 10 percent. Whenthis back plate system is incorporated into an electrochromic mirror,the predicted overall reflectance decreases and the transmittanceincreases. In this case, the values would be appropriate for anautomotive interior transflective mirror.

In a mirror construction, such as that shown in FIG. 7E, the mirrorpreferably exhibits a reflectivity of at least 35 percent, morepreferably at least 50 percent, and more preferably at least 65 percentfor an outside mirror and, for an inside mirror, the mirror preferablyexhibits a reflectance of at least 70 percent and more preferably atleast 80 percent. To obtain such reflectance levels, the reflectivesecond electrode 120 should have a slightly higher reflectance. Themirror preferably exhibits a transmittance of at least about 5 percent,more preferably at least about 10 percent, and most preferably at leastabout 15 percent. To obtain these transmittance levels, the secondelectrode 120 may have a slightly lower transmittance.

Because electrochromic mirrors having a b* value of greater than +15have an objectionable yellowish hue, it is preferable that the mirrorexhibits a b* value less than about 15, and more preferably less thanabout 10. Thus, second electrode 120 preferably exhibits similarproperties.

To obtain an electrochromic mirror having relative color neutrality, theC* value of the mirror should be less than 20. Preferably, the C* valueis less than 15, and more preferably is less than about 10. Secondelectrode 120 preferably exhibits similar C* values.

The inventors have recognized that, when a thin layer of silver orsilver alloy is used in a rearview mirror such as those described above,the thin layer may impart a light yellow hue (b* greater than +15) toobjects viewed in the reflection particularly when the thin layer ofsilver or silver alloy is made thin enough to impart sufficienttransmittance of 5 percent or more. This causes the mirror to no longerappear color neutral (C* greater than 20). Conversely, transmissionthrough the film is higher for blue light than for red light. The tenpreceding examples compensate for this liability by selection of theappropriate thicknesses of various underlayer films. Another approach tominimizing the yellow hue of the reflected images is to reflect thetransmitted blue light back through the mirror. Typically, in the priorart signal or display mirrors a coating of black paint is applied to thefourth surface of the mirror in all areas except for where a display ismounted (if one is employed). Such a black coating was designed toabsorb any light that is transmitted through the mirror and itsreflective layer(s). To minimize the yellow hue of the reflected imageappearing when a thin silver/silver alloy material is used, the blackcoating may be replaced with a coating 182 that reflects the blue lightback through the mirror rather than absorbing such blue light.Preferably, blue paint is used in place of the black paint since theblue backing reflects blue light. Alternatively, coating 182 may bewhite, gray, or a reflective coating such as chrome, since they toowould reflect blue light back through the reflective layer(s) and theremainder of the mirror.

To demonstrate the effectiveness of blue coating 182 on the fourthsurface 114 b of a mirror, an electrochromic mirror was constructed witha thin layer of silver 178 over a 100Ω/Y ITO layer 172 as the thirdsurface reflector/electrode 120. The white light reflectivity of themirror was about 52 percent, and the white light transmission was about30 percent. The mirror had a noticeably yellow hue in reflection and ablue hue in transmission. The mirror was placed on a black backgroundand the color was measured using a SP-68 Spectrophotometer from X-Rite,Inc. of Grandville, Mich. The measured b* value was +18.72. The samemirror was then placed on a blue background and the color was againmeasured. With the blue background, the measured b* value fell to +7.55.The mirror thus exhibited noticeably less yellow hue in reflection onthe blue background as compared to a black background.

Yet another variation of reflector/electrode 120 is illustrated in FIG.7F. As illustrated, reflector/electrode 120 is constructed acrosssubstantially the entire front surface 114 a of rear element 114 with anelectrically conductive multi-layer interferential thin-film coating190. Conductive thin-film coating 190 is preferably tailored to maximizetransmittance to light having wavelengths within a narrow bandcorresponding to the wavelength of light emitted from light source 170.Thus, if light source 170 were a signal light including red, red-orange,or amber AlGaAs or AlInGaP LEDs, the light emitted from such LEDs wouldhave wavelengths in the range of 585 nm to 660 nm, and conductivethin-film coating 190 would be tailored to maximize spectraltransmittance at those wavelengths. By increasing the transmittancepreferentially within this relatively narrow band of wavelengths, theaverage luminous reflectance to white light remains relatively high. Aswill be apparent from the four examples provided below of electrodesconstructed using such conductive thin-film coatings, the conductivethin-film coating as so constructed includes a first layer 184 of afirst material having a relatively high refractive index, a second layer186 of a second material formed on first layer 184 where the secondmaterial has a relatively low refractive index, and a third layer 187formed on second layer 186 and made of a material that has a relativelyhigh refractive index. Conductive thin-film coating 190 may also includea thin fourth layer 188 of an electrically conductive material formed onthird layer 187. If third layer 187 is not electrically conductive,fourth layer 188 of an electrically conductive material must be disposedon third layer 187. If the first, second, and third layers providesufficient reflectivity, such a fourth layer 188 may be made of atransparent conductive material. If not, fourth layer 188 may be made ofa reflective material.

Conductive thin-film coating 190 preferably exhibits: a luminousreflectance of 35 to 95 percent, a reflected C* value of 20 or less, asignal light/display luminous transmittance of 10 percent or more, and asheet resistance of less than 100Ω/Y. More preferably, C* is less than15 and most preferably less than 10, and the value of a* is negative. Asa measure of comparison, luminous reflection and reflected C* for thiscoating may be measured using one or more of the CIE illuminants A, B,C, or D55, D65, an equal-energy white source or other broad-band sourcemeeting the SAE definition of white. Luminous reflectance and reflectedC* for this coating may be measured at one or more angles of incidencebetween 10° and 45° from the surface normal. The signal light/displayluminous transmittance for this coating may be measured using one ormore signal or display sources such as amber, orange, red-orange, red,or deep red LEDs, vacuum fluorescent displays (VFDs), or other lamps ordisplays, and at one or more angles of incidence between 20° and 55°from the surface normal. As will be apparent to those skilled in theart, “Luminous Reflectance” and “Signal light/display LuminousTransmittance” imply use of either or both of the 1931 CIE 2 degreeobserver V_(λ) or V_(λ)′ as the eye-weighting functions.

By configuring conductive thin-film coating 190 to have a reflectance,transmittance, electrical conductivity, and a reflected C* value withinthe above parameters, an electrode may thus be constructed that hasmedium to high reflectance, substantially neutral reflectance forfaithful rendering, medium to high in-band signal light/displaytransmittance for efficiency and brightness, and low sheet resistancefor good electrochromic functionality.

In the specific examples of such a conductive thin-film coating, thefirst and third materials forming first and third layers 184 and 187,respectively, may be the same or a different material selected from thegroup consisting essentially of indium tin oxide, fluorine-doped tinoxide, titanium dioxide, tin dioxide, tantalum pentoxide, zinc oxide,zirconium oxide, iron oxide, silicon, or any other material having arelatively high refractive index. Second layer 186 may be made ofsilicon dioxide, niobium oxide, magnesium fluoride, aluminum oxide, orany other material having a low refractive index. First layer 184 mayhave a thickness of between about 200 Å to 800 Å, second layer 186 mayhave a thickness of between about 400 Å to 1200 Å, third layer 187 mayhave a thickness between about 600 Å to 1400 Å, and layer 188 may have athickness of about 150 Å to 300 Å. Other optimal thicknesses outsidethese ranges may also be obtainable per the above description. Insertingadditional layer sets of low and high index materials can raisereflectance further. Preferably, the electrically conductive materialforming fourth layer 188 is made of a reflective material such as silveror silver alloy, or of a transparent conductive material such as ITO.

According to a first example of conductive thin-film coating 190, anelectrochromic mirror was modeled having a front element 112 having athickness of 2.2 mm, a first electrode 128 made of ITO and having athickness of approximately 1400 Å, an electrochromic fluid/gel having athickness of approximately 137 to 190 microns, and a conductivethin-film coating 190 provided on a rear glass substrate 114. Conductivethin-film coating 190 in this first example included a first layer 184made of ITO and having a thickness of approximately 750 Å, a secondlayer 186 made of SiO₂ and having a thickness of approximately 940 Å, athird layer 187 made of ITO and having a thickness of approximately 845Å, and a fourth layer 188 made of silver and having a thickness of 275Å. In air, the conductive thin-film coating 190 modeled in this firstexample exhibited a luminous reflectance of approximately 80.2 percentfor white light and a spectral transmittance of approximately 22.5percent on average for light having wavelengths between 620 nm and 650nm. Such characteristics make the conductive thin-film coating 190according to this first example suitable for use either in an inside oroutside rearview mirror. When this conductive thin-film coating isapplied to the front surface of rear glass element and incorporated intoan electrochromic mirror, the overall reflectance decreases and thetransmittance increases.

According to a second example, another electrochromic mirror was modeledhaving the same features as discussed above with the exception thatconductive thin-film coating 190 included a first layer 184 made of ITOand having a thickness of approximately 525 Å, a second layer of SiO₂having a thickness of approximately 890 Å, a third layer 187 made of ITOand having a thickness of approximately 944 Å, and a fourth layer 188made of silver and having a thickness of approximately 168 Å. In air,the conductive thin-film coating as constructed in the second examplehas a luminous reflectance of approximately 63 percent for white lightincident thereupon at a 20° angle of incidence, and a spectraltransmittance of approximately 41 percent on average for light havingwavelengths in the 620 nm to 650 nm wavelength range at 20° angle ofincidence. Such a conductive thin-film coating 190 is particularlysuitable for an outside rearview mirror. When this conductive thin-filmcoating is applied to the front surface of rear glass element andincorporated into an electrochromic mirror, the overall reflectancedecreases and the transmittance increases.

A conductive thin-film coating according to a third example was modeledthat was made of the same materials as described for the first twoconductive thin-film coatings except that first layer 184 had athickness of approximately 525 Å, second layer 186 had a thickness ofapproximately 890 Å, third layer 187 had a thickness of approximately945 Å, and fourth layer 188 had a thickness of approximately 170 Å. Inair, the conductive thin-film coating thus modeled had a luminousreflectance of 63 percent at 20° angle of incidence for illuminationwith white light, and an average spectral transmittance of approximately41 percent for light having wavelengths between the 620 nm and 650 nmwavelength range at 20° angle of incidence. When this conductivethin-film coating is applied to the front surface of rear glass elementand incorporated into an electrochromic mirror, the overall reflectancedecreases and the transmittance increases.

According to a fourth example, a non-conductive three layer interferencecoating available from Libbey Owens Ford (LOF) of Toledo, Ohio, is usedin combination with a conductive fourth layer 188 of ITO or the like.The thin film stack available from LOF has a first layer 184 of Si, asecond layer 186 of SiO₂, and a third layer 187 of SnO₂. This coatinghas a reflectance of approximately 80 percent and a transmittance ofapproximately 4 percent for white light, and transmittance of 7 to 10percent for light having wavelengths in the 650 to 700 nm range. Thetransmittance in the 650 to 700 nm range makes this thin film stackparticularly suitable for a signal mirror that utilizes a red lightsource. While the SnO₂, SiO₂ and Si used in the LOF thin film stack arenot highly reflective materials by themselves (particularly when appliedas a thin layer), the alternating layers of such materials having highand low refractive indices produce the requisite high level ofreflectivity. The poor electrical conductivity of this thin film stackrequires that it be implemented with an electrically conductive layerthat has good electrical conductivity, such as a layer of ITO or thelike. The LOF thin film stack overcoated with an ITO layer having ahalf-wave thickness exhibited a sheet resistance of 12Ω/Y. When theITO/LOF thin-film stack was used as a second electrode for anelectrochromic mirror, the mirror had a reflectance of 65 percent.Several different displays were placed behind the assembled mirror andwere all easily observed.

FIG. 7G shows yet another alternate construction that is very similar tothat shown in FIG. 7F, with the exception that only three layers areutilized for the electrically conductive multi-layer thin-film coating190. According to the construction shown in FIG. 7G, thin-film coating190 includes a first layer 184 made of a material having a highrefractive index such as the materials noted above in connection withFIG. 7F, a second layer made of a material having a low refractive indexsuch as those materials also discussed above for layer 186 in FIG. 7F,and a third layer 188 of electrically conductive material. Layer 188need not be made of a material having a high refractive index, butrather may be made of any electrically conductive material suitable foruse in an electrochromic mirror. For example, layer 188 may be a highlyreflective metal, such as silver or a silver alloy, or may be a metaloxide, such as ITO. To illustrate the feasibility of such a coating, twoexamples are described below.

In a first example, an electrochromic mirror was modeled having a firstlayer 184 of ITO deposited on a front surface of rear glass substrate114 at a thickness of 590 Å, a second layer 186 of silicon dioxideapplied at a thickness of 324 Å over first layer 184, and a third layer188 of silver having a thickness of 160 Å applied over second layer 186.The electrochromic mirror was then illuminated with a CIE illuminant D65white light source at an angle of incidence of 20°. When illuminatedwith such white light, the mirror exhibited a luminance reflectance of52 percent and a* and b* values of approximately 1.0 and 5.0,respectively. When illuminated with a red LED source at 35° angle ofincidence, the mirror exhibited a luminous transmittance of 40 percent.

According to a second example of the structure shown in FIG. 7G, anelectrochromic mirror was modeled having a first layer 184 of silicondeposited at a thickness of 184 Å on the front surface of glasssubstrate 114, a second layer 186 deposited on first layer 184 andformed of silicon dioxide at a thickness of 1147 Å, and a third layer188 of ITO of a thickness of 1076 Å applied over second layer 186. Theelectrochromic mirror having such a coating was illuminated with a CIEilluminant D65 white light source at 20° angle of incidence. Whenmodeled as illuminated with such white light, the modeled mirrorexhibited a luminous reflectance of 54 percent and a* and b* values of−2.5 and 3.0, respectively. When modeled as illuminated with a red LEDsource at 35° angle of incidence, the modeled mirror exhibited aluminous transmittance of approximately 40 percent.

Considering that the above two three-layer examples exhibited luminousreflectance in excess of 50 percent and transmittance of approximately40 percent, a mirror constructed as shown in FIG. 7G meets the specificobjectives noted above with respect to FIG. 7F, and is thereforesuitable for use in an outside electrochromic rearview mirrorincorporating a signal light.

As will be apparent to those skilled in the art, the electricallyconductive multi-layer thin-film coating described above may beimplemented as a third surface reflector for an electrochromic mirrorregardless of whether the electrochromic medium is a solution-phase,gel-phase, or hybrid (solid state/solution or solid state/gel).

Although the above alternative constructions shown and described withrespect to FIGS. 7A-7G do not include a flash-over protective layer suchas layer 124 shown in FIG. 3, those skilled in the art will understandthat such a flash-over layer may be applied over any of the variousreflector/electrode 120 constructions shown in FIGS. 7A-7G.

FIG. 8 shows a cross section of one embodiment of the present inventionas similarly illustrated in FIG. 7E above. Specifically, by mounting alight emitting display assembly, indicator, enunciator, or othergraphics 170 behind a reflective layer such as layer 178, spuriousreflections occur at various interfaces within the electrochromic mirrorthat result in one or more ghost images being readily viewable by thevehicle occupants. The perceived separation between these imagesincreases as the reflective surfaces move further apart. In general, thethinner the glass used in the mirror construction, the lessobjectionable the images become. However, eliminating or reducing theintensity of the spurious reflections enhances the overall clarity ofthe display. As shown in FIG. 8, a point of illumination from display170 emits light through element 114 as illustrated by light rays A andB, which are only two of an infinite number of light rays that could betraced from any one point source. Light rays A and B are thentransmitted through transparent conductive layer 172 with little or noreflections at the interface between electrode 172 and element 114 dueto the closeness of the indices of refraction of these two components.The light then reaches the interface between transparent layer 172 andreflective layer 178, where between 10 and 20 percent of the light istransmitted through reflective layer 178 into electrochromic medium 125.A large percentage of the light intensity striking reflective layer 178is thus reflected back as illustrated by light rays C and D. Whilereflected light that is incident upon a paint layer 182 on rear surface114 b of element 114 (ray C) may be absorbed substantially in itsentirety, light that is reflected back at display 170 (ray D) is notabsorbed by the layer of absorbent paint 182. Because many lightemitting displays, such as a vacuum fluorescent display with a glass topplate, an LCD, or any other display assembly mounted such that there isan air gap between surface 114 b and the front surface of display 170,typically include at least one specular surface 171, light reflectedback at the specular surface(s) 171 of display 170 (ray D) is reflectedoff surface 171 back through element 114, reflective electrode 120,electrochromic medium 125, layers 128 and 130, and element 112. Thisspurious reflection off of the specular surface 171 of display 170 thuscreates a ghost image that is viewable by the vehicle occupants.Additional spurious reflections occur at the outer surface 112 a ofelement 112 due to the differences in refractive indices of element 112and the air surrounding the electrochromic mirror. Thus, lightrepresented by ray F is reflected back into the mirror from surface 112a and is subsequently reflected off of reflective layer 178 back thoughmedium 125, layers 128 and 130, and element 112. It is thereforedesirable to implement various measures that eliminate or reduce theintensity of these spurious reflections and thereby eliminate theannoying ghost images that are visible to the vehicle occupants. FIGS.9A-9D, which are described below, illustrate various modifications thatmay be made to reduce these spurious reflections. It should be notedthat these spurious reflections are always lower in brightness than thenonreflected image. One approach to improving the clarity of the displaywithout eliminating spurious reflections is to control the displaybrightness such that the intensity of the secondary images are below thevisual perception threshold. This brightness level will vary withambient light levels. The ambient light levels can be accuratelydetermined by photosensors in the mirror. This feedback can be used toadjust the display brightness so the secondary images are not brightenough to be objectionable.

In the embodiment shown in FIG. 9A, means 192 and 194 are provided forreducing or preventing reflections from specular surface 171 and frontsurface 112 a of element 112, respectively. Anti-reflective means 192may include an anti-reflective film applied to the rear surface 114 b ofelement 114 or to any and all specularly reflecting surfaces of displayassembly 170. Anti-reflective means 192 may also include a lightabsorbing mask applied to rear surface 114 b or specular surface 171 ofdisplay assembly 170. Such a masking layer 192 may be made to coversubstantially the entirety of specular surface 171, with the exceptionof those regions lying directly over a light emitting segment of display170. The masking may be made with any light absorbing material, such asblack paint, black tape, black foam backing, or the like. It should benoted that vacuum florescent displays are available with an internalblack mask in all areas around the individual light emitting elements.If anti-reflective means 192 is formed as an anti-reflective layer,substantially any known anti-reflective film may be employed for thispurpose. The anti-reflective film need only be constructed to preventreflections at the particular wavelength of the light emitted fromdisplay 170.

By providing anti-reflective means 192 as described above, any lightthat is reflected back from reflective layer 178 toward specular surface171 of display 170 is either absorbed or transmitted into display 170,such that it cannot be reflected from surface 171 through the devicetowards the eyes of the vehicle occupants. It should be noted thatanti-reflective means 192 may also include any other structure capableof reducing or preventing the reflection of light from specular surface171. Further, anti-reflective means 192 may include a combination of ananti-reflective film and a masking layer and layer 192 may beincorporated on any specularly reflective surface that could reflectlight reflected off reflector 178, for example, either the back surfaceof glass element 114, the front surface of display 170, or any internalsurface in display 170.

To reduce the spurious reflections from the air interface with surface112 a of element 112, an anti-reflective film 194 may be provided onsurface 112 a. Anti-reflective film 194 may be formed of anyconventional structure. A circular polarizer inserted between thetransflective coating and the display is also useful in reducingspurious reflections.

FIG. 9B shows an alternative solution to the problems relating to thereflection of light from display 170 off of reflective layer 178 and thespecular surface of the display. Specifically, display 170 is preferablyselected from those displays that do not include any form of specularsurface. Examples of such displays are available from Hewlett Packardand are referenced as the HDSP Series. Such displays generally have afront surface that is substantially light absorbing, such that little ifany light would be reflected off the forward-facing surface of thedisplay.

Another example of a display construction that would not have aspecularly reflecting surface (such as between glass and air) would be aback lit liquid crystal display (LCD) that is laminated directly ontothe back mirror surface 114 b to eliminate the air gap or air interfacebetween the display and the mirror. Eliminating the air gap is aneffective means of minimizing the first surface reflection of alldisplay devices. If the type of LCD used was normally opaque or darksuch as with a twisted nematic LCD with parallel polarizers or a phasechange or guest host LCD with a black dye, the reflected light would beabsorbed by the display and not re-reflected back toward the viewer.Another approach would be to use a back lit transmissive twisted nematicLCD with crossed polarizers. The entire display area would then beilluminated and contrasted with black digits. Alternatively, a positiveor negative contrast electrochromic display could be used in place ofthe LCD, or an organic LED could be laminated or fixed to the backsurface 114 b.

An alternative solution is shown in FIG. 9C, whereby display 170 ismounted in back of rear surface 114 b of rear element 114, such thatspecular surface 171 is inclined at an angle to rear surface 114 b. Asapparent from the ray tracings in FIG. 9C, any light emitted fromdisplay 170 that reflects off of reflective layer 178 back towardspecular surface 171 of display 170 is reflected off of specular surface171 at an angle which could direct the light beam away from the viewertowards, for instance, the roof of the vehicle or, if the angle of thedisplay is great enough, the beam could be directed toward an absorbingsurface such as a black mask applied to the back of the mirror onsurface 114 b. It should be noted that, rather than angling the display,the reflected beam could be deflected by some other means such as bylaminating a transparent wedge shape on the front of the display, thegoal being to redirect the reflected light out of the viewing cone ofthe display or to an absorbing media or surface.

As shown in FIG. 9E, another useful technique to reduce spuriousreflections is to reflect the display image off of a mirror surface 197(preferably a first surface mirror) at about a 45° angle and thenthrough the transflective layer 120. The image reflected off thetransflective layer 120 can then be redirected away from the specularsurfaces on the display by slightly angling the relationship of thedisplay to the transflective layer.

FIG. 9D shows yet another approach for overcoming the problems notedabove. Specifically, the embodiment shown in FIG. 9D overcomes theproblem by actually mounting the display in front of reflective layer178. To enable the display to be mounted in front of the reflectedlayer, a substantially transparent display, such as an organic lightemitting diode (OLED) 196 is utilized. OLEDs are available fromUniversal Display Corporation. Such OLEDs can be constructed such thatthey are thin transparent displays that could be mounted inside thechamber in which the electrochromic medium is maintained. Because OLED196 can be transparent, it would not interfere with the image viewed bythe driver of the vehicle. Additionally, by providing OLED 196 insidethe chamber between the substrates, display 196 is protected from anyadverse environmental effects. Thus, such an arrangement is particularlydesirable when mounting a display device in an exterior automotiverearview mirror. OLED 196 could be mounted on layer 178, layer 128,between layers 128 and 130, between layer 130 and element 112, betweenlayers 172 and 178, between layer 172 and element 114, to rear surface114 b of element 114, or to surface 112 a of element 112. Preferably,OLED display 196 is mounted in front of reflective layer 178 in thechamber between elements 112 and 114.

To take advantage of the fact that the reflective layer in anelectrochromic mirror may be partially transmissive over its entiresurface area, a light collector may be employed behind the reflectivelayer to collect the light impinging on the mirror over a much largerarea than previously possible and to amplify the light as it is directedonto a photosensor. As will be described in more detail below, the useof such a light collector more than compensates for the lack of theprovision of an opening in the reflective layer and actually canincrease the sensitivity of the glare sensor in an electrochromicmirror.

FIG. 10 is a front view of an inside rearview mirror constructed inaccordance with the present invention. FIG. 11 is a cross-sectional viewtaken along plane 11-11′ of FIG. 10. According to this construction, thelight collector may be constructed as a plano-convex lens 609 mountedbehind a partially transmissive reflecting surface 607 and a variableattenuating layer 608. As shown in FIG. 11, lens 609 projects light fromsource 601 onto focal point 604 and light from source 601 a onto focalpoint 604 a. A small area sensor, for example, the single pixel sensorof U.S. patent application Ser. No. 09/237,107, filed on Jan. 25, 1999,which is incorporated herein by reference, is provided to sense glarefrom the rear viewed through lens 609, partially transmissive layer 607,and optionally through variable attenuating layer 608. This constructiontakes advantage of the fact that the active sensing area of sensor 605is small, for example, 100 microns on a side, and that a relativelylarge light collector, lens 609 in this example, can be substantiallyhidden behind the partially transmissive mirror and configured so thatrelatively high optical gain may be provided for the sensor while stillproviding a characterized and relatively large field of view over whichglare is sensed. In the example shown in FIG. 11, light source 601 a isapproximately 20 degrees off of the central axis and is close to theedge of the amplified field of view. Note that unamplified light, partof which may not pass through the lens, may be used to maintain somesensitivity to glare over a larger field of view.

When designing a construction such as those shown in FIGS. 10 and 11,there are several design considerations. Because the source of lightthat impinges upon the mirror and creates glare is the head lamps ofautomobiles to the rear of the vehicle, and such light sources are at agreat distance away from the mirror relative to the size of the lens,the rays from an automotive head lamp light source are substantiallyparallel. With a good lens, most of the rays impinging on the lens froma source are projected to a relatively small, intense spot at the focalpoint 604. For a sensing position other than at the focal point, as afirst approximation, the optical gain is the ratio of the area of thelens through which light enters to that of the cross section of thefocused cone in the plane where the light is sensed. In FIG. 11, with aspherical or aspherical lens 609, this would be the square of the ratioat the diameter of lens 609 to the length of line 610. This isapproximately 10 as depicted. If sensor 605 was placed at the focalpoint 604 as it would be if it were a pixel in an imaging array, nearlyall of the light passing through the lens from light source 601 wouldstrike sensor 605, making the optical gain very high. However, lightfrom a light source 601 a would totally miss the sensor and the field ofview would be extremely small. In FIG. 11, sensor 605 is placed at ahighly de-focussed point, which is common to the cones of light fromlight sources having positions for which optical gain should bemaintained. Note that the plane can optionally be chosen beyond thefocal point or other methods of diffusion may be used alone or incombination to widen and characterize the field of view. For asubstantially greater off-axis angle, the sensor will be outside of theprojected cone of light and no optical gain will be provided. Note thatto provide relatively high optical gain over a substantial field ofview, the collecting area should be quite large compared to the sensor.The area of the aperture should exceed the area of the sensor first byapproximately the ratio of the optical gain, and this ratio should bemultiplied by another large factor to provide a field of view having asolid angle that is much larger than that which would be imaged onto thesensor were it to be placed in the focal plane of the lens.

While this particular mirror construction has been described above asincluding a spherical or an aspherical lens 609, a Fresnel lens mayreplace the plano-convex lens depicted. Additionally, since for largefields of views the light rays must be redirected through even largerangles, totally internally reflecting (TIR) lenses or reflectors may beused and provide additional advantages. If, for example, a partiallytransmissive reflecting layer 607 with 20 percent transmission is chosenand an optical gain of 10 is used, the optical gain more than recoversthe loss incurred in passing through partially transmissive reflector607. Furthermore, no unsightly or expensive-to-produce aperture windowneeds to be provided for the sensor and control benefits of viewingthrough the layer are also realized.

In configurations where the viewing angle needs to be large in onedirection but relatively small in another, a cylindrical lens may beused. For example, to sense lights from vehicles in adjacent lanes, theviewing angle must be relatively large in the horizontal direction andthe viewing field may be relatively narrow in the vertical direction. Inthis case, lens 609 may be replaced by a cylindrical lens with ahorizontal axis. A stripe of light rather than a circle is projected,and since light gathering takes place in one rather than two directions,the benefit of the squaring effect for the relative areas of the lensaperture in the area of the projected light pattern in the plane of thesensor is lost. Optical gains of 5, for example, are still feasible,however. Composite lenses containing a patchwork of different elementsincluding, for example, sections of aspheric lenses with differentcenter positions and/or focal lengths, or even combinations of differentkinds of elements such as aspheric and cylindrical lenses may be used toretain reasonable optical gain and characterize the field of view. A rowof lens sections with stepped focal center points can serve well towiden the field of view in selected directions while maintaining a goodoverall optical gain. Some amount of diffusion is preferable in all thedesigns to prevent severe irregularity in the sensed light level due tosevere localized irregularities in the projected light pattern that areoften present. The extremely small area sensor will not average theseirregularities to any useful degree. Some lens designs may optionally becemented to the back of the mirror element.

In each of the constructions described above with respect to FIGS. 10and 11, any of the mirror constructions described above with respect toFIGS. 7A-7G may be employed for use as the electrochromic mirror(depicted as layers 607 and 608 in FIG. 11).

FIG. 12 shows an outside rearview mirror assembly 200 constructed inaccordance with another embodiment of the present invention. Outsiderearview mirror assembly 200 includes a mirror 210, which is preferablyan electrochromic mirror, an external mirror housing 212 having amounting portion 214 for mounting mirror assembly 200 to the exterior ofa vehicle, and a signal light 220 mounted behind mirror 210. To enablethe light from signal light 220 to project through electrochromic mirror210, a plurality of signal light areas 222 are formed in theelectrode/reflector of mirror 210 that include window regions containingelectrically conductive material that is at least partially transmissivesimilar to the information display and glare sensor window areasdescribed above with respect to the other embodiments of the presentinvention. Electrochromic mirror 210 may further include a sensor area224 disposed within the reflective coating on electrochromic mirror 210and similarly include window regions containing electrically conductivematerial that is at least partially transmissive so as to allow some ofthe incident light to reach a sensor mounted behind sensor area 224.Alternatively, sensor 224 could be used to sense glare in night drivingconditions and control the dimming of the exterior mirror independentlyor verify that the mirrors are being sufficiently dimmed by the controlcircuit in the interior mirror. In such a case, a more sensitive photosensor may be required, such as a CdS sensor.

Signal light 220 is preferably provided to serve as a turn signal lightand is thus selectively actuated in response to a control signalgenerated by a turn signal actuator 226. The control signal is thereforeapplied to signal light 220 as an intermittent voltage so as to energizesignal light 220 when a driver has actuated the turn signal lever. Asshown in FIG. 15, when vehicle B is in the blind spot of vehicle A wherethe driver of vehicle A cannot see vehicle B, the driver of vehicle Bcannot see the turn signal on the rear of vehicle A. Thus, if the driverof vehicle A activates the turn signal and attempts to change laneswhile vehicle B is in a blind spot, the driver of vehicle B may notreceive any advance notice of the impending lane change, and hence, maynot be able to avoid an accident. By providing a turn signal light in anoutside rearview mirror assembly 200 of vehicle A, the driver of anapproaching vehicle B will be able to see that the driver of vehicle Ais about to change lanes and may thus take appropriate action morequickly so as to avoid an accident. As illustrated in FIG. 15 anddescribed in more detail below, the signal light is preferably mountedwithin mirror assembly at an angle to the mirror surface to project thelight from the signal light outward into the adjacent lanes in the blindspot areas proximate the vehicle.

Referring again to FIG. 12, electrochromic mirror 220 may be controlledin a conventional manner by a mirror control circuit 230 provided in theinside rearview mirror assembly. Inside mirror control circuit 230receives signals from an ambient light sensor 232, which is typicallymounted in a forward facing position on the interior rearview mirrorhousing. Control circuit 230 also receives a signal from a glare sensor234 mounted in a rearward facing position of the interior rearviewmirror assembly. Inside mirror control circuit 230 applies a controlvoltage on a pair of lines 236 in a conventional manner, such that avariable voltage is applied essentially across the entire surface ofelectrochromic mirror 210. Thus, by varying the voltage applied to lines236, control circuit 230 may vary the transmittance of theelectrochromic medium in mirror 210 in response to the light levelssensed by ambient sensor 232 and glare sensor 234. As will be explainedfurther below, an optional third control line 238 may be connectedbetween the inside mirror control circuit 230 and a variable attenuator260 provided in outside mirror assembly 200, so as to selectivelyattenuate the energizing signal applied on lines 228 from turn signalactuator 226 to the signal light 220 in response to the control signalsent on line 238. In this manner, inside mirror control circuit 230 mayselectively and remotely control the intensity of signal light 220 basedupon information obtained from sensors 232 and 234 and thereby eliminatethe need for a sensor to be mounted in each mirror assembly as well asthe associated sensor area 224.

Mirror assembly 200 may further include an electric heater (not shown)provided behind mirror 210 that is selectively actuated by a heatercontrol circuit 240 via lines 242. Such heaters are known in the art tobe effective for deicing and defogging such external rearview mirrors.Mirror assembly 200 may optionally include a mirror position servomotor(not shown) that is driven by a mirror position controller 244 via lines246. Such mirror position servomotors and controls are also known in theart. As will be appreciated by those skilled in the art, mirror assembly200 may include additional features and elements as are now known in theart or may become known in the future without departing from the spiritand scope of the present invention.

An exemplary signal light subassembly 220 is shown in FIG. 13. Such asignal light 220 is disclosed in U.S. Pat. Nos. 5,361,190 and 5,788,357,which disclose the signal light in combination with dichroic exteriorrearview mirrors that are not electrochromic. The disclosures of thesignal light assembly in U.S. Pat. Nos. 5,361,190 and 5,788,357 isincorporated herein by reference. As explained below, however, the samesignal light subassembly may be used in connection with anelectrochromic mirror as may modified versions of the signal lightsubassembly shown in FIG. 13.

As shown in FIG. 13, signal light 220 includes a printed circuit board250 that, in turn, is mounted within a housing 252 having a peripheraledge that serves as a shroud (see FIGS. 6A and 6B) to block any straylight from exiting the signal light assembly. Signal light 220preferably includes a plurality of LEDs 254 that are mounted to circuitboard 250. LEDs 254 may be mounted in any pattern, but are preferablymounted in a pattern likely to suggest to other vehicle operators thatthe vehicle having such signal mirrors is about to turn. LEDs 254 may beLEDs that emit red or amber light or any other color light as may provedesirable. LEDs 254 are also preferably mounted to circuit board 250 atan angle away from the direction of the driver. By angling LEDs relativeto mirror 210, the light projected from LEDs 254 may be projectedoutward away from the driver towards the area C in which the driver ofanother vehicle would be more likely to notice the signal light, asshown in FIG. 15. Hence, the potential glare from the signal light asviewed by the driver may be effectively reduced.

Signal light 220 may optionally include a day/night sensor 256 alsomounted to circuit board 250. If sensor 256 is mounted on circuit board250, a shroud 257 is also preferably mounted to shield sensor 256 fromthe light generated by LEDs 254. Also, if sensor 256 is provided insignal light 220, a day/night sensing circuit 258 may also be mounted oncircuit board 250 so as to vary the intensity of LEDs 254 in response tothe detection of the presence or absence of daylight by sensor 256.Thus, if sensor 256 detects daylight, circuit 258 increases theintensity of the light emitted from LEDs 254 to their highest level anddecreases the intensity of the emitted light when sensor 256 detectsthat it is nighttime. The above-noted signal light disclosed in U.S.Pat. Nos. 5,361,190 and 5,788,357 includes such a day/night sensor 256and associated control circuit 258, and therefore, further descriptionof the operation of the signal light in this regard will not beprovided.

As an alternative to providing a day/night sensor 256 in each of thevehicle's exterior rearview mirrors, a variable attenuator 260 or othersimilar circuit may be provided to vary the driving voltage applied fromthe turn signal actuator 226 on line 228 in response to a control signaldelivered from inside mirror control circuit 230 on a dedicated line238. In this manner, inside mirror control circuit 230 may utilize theinformation provided from ambient light sensor 232 as well as theinformation from glare sensor 234 to control the intensity of the lightemitted from LEDs 254 and signal light 220. Since the ambient light andglare sensors 232 and 234 are already provided in an internalelectrochromic rearview mirror, providing for such remote control by theinside mirror control circuit 230 eliminates the need for providingadditional expensive sensors 256 in the signal light 220 of eachexterior mirror assembly. As an alternative to running a separate wire258 to each of the outside rearview mirrors, variable attenuator 260 maybe provided in the dashboard proximate the turn signal actuator orotherwise built into the turn signal actuator, such that a singlecontrol line 238′ may be wired from inside mirror control circuit 230 tothe turn signal actuator as shown in FIG. 12.

The intensity of the light emitted from the LEDs may thus be varied as afunction of the light level sensed by ambient sensor 232 or glare sensor234, or as a function of the light levels sensed by both sensors 232 and234. Preferably, LEDs 254 are controlled to be at their greatestintensity when ambient sensor 232 detects daylight and at a lesserintensity when sensor 232 detects no daylight. Because the transmittanceof the electrochromic medium is decreased when excessive glare isdetected using glare detector 234, the intensity of LEDs 254 ispreferably correspondingly increased so as to maintain a relativelyconstant intensity at nighttime.

Electrochromic mirror 210 may be constructed in accordance with any ofthe alternative arrangements disclosed in FIGS. 7A-7F above, where lightsource 170 represents one of LEDs 254 of signal light subassembly 220.Accordingly, each possible combination of the various constructionsshown in FIGS. 7A-7F with signal light subassembly 220 are notillustrated or described in further detail. As but one example, however,FIG. 14 shows the manner in which a signal light subassembly 220 couldbe mounted behind a preferred construction that is otherwise identicalto that shown in FIG. 7C. As apparent from a comparison of FIG. 7C andFIG. 14, each of signal light areas 222 corresponds to window 146 ofFIG. 7C. As discussed above, for an outside rearview mirror thereflectance of reflector/electrode 120 is preferably at least 35 percentand the transmittance is preferably at least 20 percent so as to meetthe minimum reflectance requirements and yet allow sufficienttransmittance so that the light emitted from signal light 220 may bereadily noticed by the driver of an approaching vehicle.

FIG. 16 shows a front elevational view schematically illustrating aninside mirror assembly 310 according to an alternative embodiment of thepresent invention. Inside mirror assembly 310 may incorporatelight-sensing electronic circuitry of the type illustrated and describedin the above-referenced Canadian Patent No. 1,300,945, U.S. Pat. No.5,204,778, or U.S. Pat. No. 5,451,822, and other circuits capable ofsensing glare and ambient light and supplying a drive voltage to theelectrochromic element.

Rearview mirrors embodying the present invention preferably include abezel 344, which conceals and protects the spring clips (not shown) andthe peripheral edge portions of the sealing member and both the frontand rear glass elements (described in detail below). Wide varieties ofbezel designs are well known in the art, such as, for example, the bezeldisclosed in above-referenced U.S. Pat. No. 5,448,397. There is also awide variety of known housings for attaching the mirror assembly 310 tothe inside front windshield of an automobile; a preferred housing isdisclosed in above-referenced U.S. Pat. No. 5,337,948.

The electrical circuit preferably incorporates an ambient light sensor(not shown) and a glare light sensor 360, the glare light sensor beingcapable of sensing glare light and being typically positioned behind theglass elements and looking through a section of the mirror with thereflective material partially removed in accordance with this particularembodiment of the present invention. Alternatively, the glare lightsensor can be positioned outside the reflective surfaces, e.g., in thebezel 344. Additionally, an area or areas of the third surfacereflective electrode, such as 346, may be partially removed inaccordance with the present invention to permit a display, such as acompass, clock, or other indicia, to show through to the driver of thevehicle. The present invention is also applicable to a mirror which usesonly one video chip light sensor to measure both glare and ambient lightand which is further capable of determining the direction of glare. Anautomatic mirror on the inside of a vehicle, constructed according tothis invention, can also control one or both outside mirrors as slavesin an automatic mirror system.

FIG. 17 shows a cross-sectional view of mirror assembly 310 along theline 17-17′. Like the above-described embodiments, mirror 310 has afront transparent element 112 having a front surface 112 a and a rearsurface 112 b, and a rear element 114 having a front surface 114 a and arear surface 114 b. Since some of the layers of the mirror are verythin, the scale has been distorted for pictorial clarity. A layer of atransparent electrically conductive material 128 is deposited on thesecond surface 112 b to act as an electrode. Transparent conductivematerial 128 may be any of the materials identified above for the otherembodiments. If desired, an optional layer or layers of a colorsuppression material 130 may be deposited between transparent conductivematerial 128 and front glass rear surface 112 b to suppress thereflection of any unwanted portion of the electromagnetic spectrum.

At least one layer of a material that acts as both a reflector and aconductive electrode 120 is disposed on third surface 114 a of mirror310. Any of the materials/multi-layer films described above maysimilarly be used for reflector/electrode 120. U.S. Pat. No. 5,818,625entitled “DIMMABLE REARVIEW MIRROR INCORPORATING A THIRD SURFACE METALREFLECTOR” and filed on or about Apr. 2, 1997, describes anotherreflector/electrode 120 in detail. The entire disclosure of this patentis incorporated herein by reference.

In accordance with this embodiment of the present invention, a portionof conductive reflector/electrode 120 is removed to leave an informationdisplay area 321 comprised of a non-conducting area 321 a (to view adisplay) and a conducting area 321 b (to color and clear theelectrochromic medium), as shown in FIG. 17. Although only shown indetail for the display area 321, the same design may be, and preferablyis, used for the glare sensor area (160 in FIG. 16). FIG. 18 shows afront elevational view illustrating information display area 321. Again,since some of the layers of this area are very thin, the scales of thefigures have been distorted for pictorial clarity. The portion ofconductive reflector/electrode that is removed 321 a is substantiallydevoid of conductive material, and the portion not removed should be inelectrical contact with the remaining area of reflector/electrode 120.That is to say, there are little or no isolated areas or islands ofreflector/electrode 120 that are not electrically connected to theremaining portions of the reflector/electrode 120. Also, although theetched areas 321 a are shown as U-shaped (FIG. 17), they may have anyshape that allows sufficient current flow through lines 321 b whileallowing the driver to view and read the display 170 through etchedareas 321 a. The reflector/electrode 120 may be removed by varyingtechniques, such as, for example, by etching (laser, chemical, orotherwise), masking during deposition, mechanical scraping,sandblasting, or otherwise. Laser etching is the presently preferredmethod because of its accuracy, speed, and control.

The information display area 321 is aligned with a display device 170such as a vacuum fluorescent display, cathode ray tube, liquid crystal,flat panel display and the like, with vacuum fluorescent display beingpresently preferred. The display 170, having associated controlelectronics, may exhibit any information helpful to a vehicle occupant,such as a compass, clock, or other indicia, such that the display willshow through the removed portion 321 a to the vehicle occupant.

The area that is substantially devoid of conductive reflector/electrode321 a and the area having conductive reflector/electrode present 321 bmay be in any shape or form so long as there is sufficient area havingconductive material to allow proper coloring and clearing (i.e.,reversibly vary the transmittance) of the electrochromic medium, whileat the same time having sufficient area substantially devoid ofconductive material to allow proper viewing of the display device 170.As a general rule, information display area 321 should haveapproximately 70-80 percent of its area substantially devoid ofconductive material 321 a and the conductive material 321 b filling theremaining 20-30 percent. The areas (321 a and 321 b) may have a varietyof patterns such as, for example, linear, circular, elliptical, etc.Also, the demarcation between the reflective regions and the regionsdevoid of reflective material may be less pronounced by varying thethickness of the reflective materials or by selecting a pattern that hasa varying density of reflective material. It is presently preferred thatareas 321 a and 321 b form alternating and contiguous lines (see FIG.17). By way of example, and not to be construed in any way as limitingthe scope of the present invention, the lines 321 b generally may beapproximately 0.002 inch wide and spaced approximately 0.006 inch apartfrom one another by the lines substantially devoid of conductivematerial. It should be understood that although the figures show thelines to be vertical (as viewed by the driver), they may be horizontalor at some angle from vertical. Further, lines 321 a need not bestraight, although straight vertical lines are presently preferred.

If all of the third surface reflector/electrode 120 is removed in theinformation display area 321 or in the area aligned with the glare lightsensor 160, there will be significant coloration variations betweenthose areas and the remaining portion of the mirror where thereflector/electrode 120 is not removed. This is because for everyelectrochromic material oxidized at one electrode there is acorresponding electrochromic material reduced at the other electrode.The oxidation or reduction (depending on the polarity of the electrodes)that occurs on the second surface directly across from the informationdisplay area 321 will occur uniformly across the area of the informationdisplay area. The corresponding electrochemistry on the third surfacewill not, however, be uniform. The generation of light-absorbing specieswill be concentrated at the edges of the information display area (whichis devoid of reflector/electrode). Thus, in the information display area321, the generation of the light-absorbing species at the second surfacewill be uniformly distributed, whereas the light-absorbing species atthe third surface will not, thereby creating aesthetically unappealingcolor discrepancies to the vehicle occupants. By providing lines ofreflector/electrode 120 areas throughout the information display area321, in accordance with the present invention, the generation oflight-absorbing species (at the second and third surfaces) in theinformation display area will be much closer to the uniformity seen inother areas of the mirror with completely balanced electrodes.

Although those skilled in the art will understand that manymodifications may be made, the laser etching may be accomplished byusing a 50 watt Nd:YAG laser, such as that made by XCEL Control Laser,located in Orlando, Fla. In addition, those skilled in the art willrealize that the power settings, the laser aperture, the mode of thelaser (continuous wave or pulsed wave), the speed with which the lasermoves across the surface, and the wave form of the laser may be adjustedto suit a particular need. In commercially available lasers, there arevarious wave forms that the laser follows while it ablates the surfacecoatings. These wave forms include straight lines, sine waves at variousfrequencies and ramp waves at various frequencies, although many othersmay be used. In the presently preferred embodiments of the presentinvention, the areas devoid of reflective material 321 a are removed byusing the laser in a pulsed wave mode with a frequency of about 3 kHz,having a narrow (e.g., around 0.005 inch) beam width where the laser ismoved in a straight line wave form.

FIGS. 14B and 14C show two alternate arrangements for implementing thepresent invention. FIGS. 14B and 14C are partial cross-sectional viewstaken along lines 14-14′ of FIG. 12. FIG. 14B shows an arrangementsimilar to that of the inside rearview mirror shown in FIG. 17 in whichparallel lines of reflector/electrode material 222 b are provided acrossthe signal light area 222 by either etching out or masking lines 222 ain regions that are devoid of the reflector/electrode material. Each ofthe signal light areas 222 is provided in a position on the rearviewmirror corresponding and overlying one of LEDs 254 as apparent from acomparison of FIGS. 12 and 13. Electrochromic mirror 410 may beconstructed in the same manner as described above for the insiderearview mirror 310 of the preceding embodiment. Specifically, mirror410 includes a front transparent element 112 having a front surface anda rear surface, and a rear element 114 having a front surface 114 a anda rear surface 114 b. Mirror 410 also includes a layer 128 of atransparent conductive material deposited on the rear surface of frontelement 112 or on an optional color suppression material 130 that isdeposited on the rear surface of front element 112. Additionally, mirror410 includes at least one layer 120 disposed on a front surface 114 a ofrear element 314 that acts as both a reflector and a conductiveelectrode. An electrochromic medium is disposed in a chamber definedbetween layers 128 and 120. All of the component elements of mirror 410may be made using the same materials and applied using the sametechniques as described above with respect to the preceding embodiments.Preferably, however, the reflector/electrode material of layer 120 ismade using nickel, chrome, rhodium, stainless steel, silver, silveralloys, platinum, palladium, gold, or combinations thereof.

The reflectance of the mirror in the signal light areas 222 or sensorarea 224 may also be controlled by varying the percentage of those areasthat are devoid of reflective material or by varying the thickness ofthe reflector/electrode coating. Further, the reflector/electrodematerial used to form lines 222 b in signal light area may be differentfrom the reflector/electrode material used for the remainder of themirror. For example, a reflector/electrode material having a higherreflectance may be used in the signal light area such that thereflectivity in the signal light area is the same as that of theremainder of the mirror despite the regions therein that are devoid ofreflector material. Preferably, the region of the signal light area thatis devoid of reflective material constitutes between 30 and 50 percentof the signal light area and the area occupied by the reflectivematerial is between 50 and 70 percent of the signal light area. Toachieve these percentages, the lines of reflector/electrode material arepreferably about 0.010 inch wide and the spaces between the lines areabout 0.006 inch wide.

The arrangement shown in FIG. 14C differs from that shown in FIG. 14B inthat the reflective material is formed on the fourth surface (i.e., therear surface 114 b of rear element 114). With such an arrangement, theelectrode 340 on the third surface is preferably made of a transparentmaterial similar to that of the electrode 128 formed on the rear surfaceof front element 112. Like the arrangement shown in FIG. 14B, thestructure shown in FIG. 14C includes a signal light area 222 havingalternating regions of reflective material 222 b and regions devoid ofsuch reflective material 222 a. In this manner, LEDs 254 may be morecovertly hidden from view by the driver and yet light from LEDs 254 mayproject through all the layers of electrochromic mirror 410 so as to bevisible by drivers of other vehicles. Similarly, if a day/night sensor256 is provided, a sensor area 224 may be provided in the same mannerwith alternating regions of reflective material 224 b and regions thatare void of reflective material 224 a.

A benefit of utilizing the above-described structure in connection witha signal light is that the use of a dichroic coating may be avoided.Dichroic coatings are generally nonconductive and therefore cannot beused in an electrochromic mirror having a third surface reflector. Also,the only current dichroic coatings that are economically feasible arethose that transmit red and infrared light and reflect other colors oflight. Thus, to construct a practical signal light, only LEDs that emitred light may be utilized. Accordingly, there is little flexibility inthis regard when a dichroic coating is utilized. To the contrary, withthe structure of the present invention, any color signal light may beused.

The concept of providing a window region having alternating areas devoidof reflective material may similarly be applied to a non-electrochromicsignal mirror. And although other materials may be used, chromium on thefirst or second surface of such a non-electrochromic mirror is thepresently preferred reflective material.

FIGS. 14D and 19 show yet another embodiment of the present invention asit pertains to signal mirrors. According to this embodiment, the signalmirror includes an additional structure for rendering the signal lightmore covert with respect to the field of view of the driver. While eachof the embodiments relating to the signal mirrors discussed abovecovertly hides the signal light behind the mirror when they are notenergized and generally hides the signal light when activated, thereremains the possibility with such embodiments that the driver may bedistracted during the periods in which the signal light is activated.Specifically, while the LEDs of the signal light are angled outward awayfrom the driver's eyes, the driver may still be able to see the LEDs aspoints of light through portions of the mirror assembly. Accordingly,this embodiment provides means for reducing the transmission of lightfrom the signal light through the mirror in the direction of the driver.As explained below, this additional means may take on severalalternative or additive forms.

Referring to FIG. 14D, a construction is shown whereby a baffle assembly500 is positioned between signal light assembly 220 and the rear surfaceof mirror assembly 510. The particular baffle assembly 500 shown in FIG.14D includes a forward, upper plate 502 and a rearward, lower plate 504fixed in spaced and parallel relation by a plurality of legs 506. Asillustrated in FIGS. 14D and 19, lower plate 504 is laterally displacedrelative to forward plate 502 in a more outward position away from thedriver. Lower plate 504 includes a plurality of apertures 508corresponding in size and position to each of LEDs 254. Upper plate 502is disposed relative to aperture 508 and slightly over LEDs 254 so as toblock the driver's view of LEDs 254. Upper plate 502 includes anaperture 509 through which light may pass so as to reach sensor 256. Thespaces between upper plate 502 and lower plate 504 as well as apertures508 in lower plate 504 provide a sufficient opening for light projectedfrom the angled LEDs 254 to be transmitted through mirror 510 and intoregion C shown in FIG. 15. Baffle assembly 500, as shown, is preferablymade of a black plastic or the like.

The functionality of baffle assembly 500 may be supplemented oralternatively performed by various other mechanisms designated generallyin FIG. 14D by reference numeral 520. Specifically, element 520 may beany one or a combination of a light control film, a layer of black ordark paint, or a heater element. A light control film, such as thatavailable from the 3M Company under the trade designation LCF-P, may beused, which is a thin plastic film enclosing a plurality of closelyspaced, black colored microlouvers. Such a light control film isdisclosed for use in a conventional signal mirror in U.S. Pat. Nos.5,361,190 and 5,788,357, the disclosures of which are herebyincorporated by reference. As disclosed in those patents, such a lightcontrol film may have a thickness of 0.030 inches, with the microlouversspaced approximately 0.005 inches apart. The microlouvers are typicallyblack and are positioned at various angular positions to provide asuitable viewing angle. Such a light control film permits light fromLEDs 254 to be transmitted at the appropriate viewing angle to reachregion C (FIG. 15). The light control film also serves to block thelight projected from LEDs 254 from travelling outside the appropriateviewing angle in the line of sight of the driver. Thus, unlike thebaffle assembly 500 depicted in FIGS. 14D and 19, such a light controlfilm may be placed completely over and in front of each of LEDs 254.Further, such a light control film could also be made using other formsof optical elements, such as holograms and the like.

If element 520 is a coating of an opaque paint, such a coating would notextend far enough in front of the LEDs to block light from LEDs 254 tobe transmitted through mirror 510 into blind spot area C (FIG. 15).Alternatively, such a coating of paint could extend completely in frontof LEDs 254, provided it was configured to have some form of louver orequivalent structure formed in its surface in the areas of the intendedtransmission path of LEDs 254. For example, the thickness of such apaint coating could be controlled to create effective louvers usingscreen-printing, molding, stamping, or laser ablation. Further, ifreflector/electrode 120 is configured in the manner described above withrespect to FIGS. 14B and 14C, element 520 could be a coating of blackpaint that has similar bars or stripes in the areas overlying LEDs 254while having spatial relations relative to the bars 222 b ofreflector/electrode 120, so as to provide a transmission path at theappropriate angle for vehicles to view the lights when in the vehicle'sblindspots, while blocking the light from the field of view of thedriver. Further, as shown in FIG. 14D, the bars 222 b ofreflector/electrode 120 may be configured to have varying widths thatdecrease with increasing distance from the driver, so as to reduceperipheral transmittance through area 222 in the direction of thedriver, or may have a less pronounced edge definition, as discussedabove.

If element 520 is provided using a mirror heating element, the heatingelement could be provided to extend across the entire fourth surface ofthe mirror and have apertures formed in appropriate locations to allowlight emitted from LEDs 254 to be transmitted at the appropriate angle.

Another mechanism for shielding the driver from light emitted from LEDs254 is to increase the thickness of the reflector/electrode 120 in aregion 530 corresponding to that of upper plate 502 thereby reducing thetransmittance through that portion of reflector/electrode 120.Currently, such reflector/electrodes have a transmittance ofapproximately 1-2 percent. To sufficiently shield the driver from lighttransmitted from LEDs 254, reflector/electrode 120 preferably has athickness in region 530 that reduces the transmittance therethrough toless than 0.5 percent, and more preferably to less than 0.1 percent.

Element 520 may additionally or alternately include various opticalfilms, such as a prismatic or Fresnel film or a collimating opticalelement as described in U.S. Pat. No. 5,788,357 so as to collimate anddirect the light emitted from LEDs 254 at the appropriate angle withoutalso transmitting light in the direction of the driver.

As yet another possible solution, sidewalls 252 of light assembly 220may be extended so as to space LEDs 254 further from the rear surface ofmirror assembly 510, such that sidewalls 252 effectively block any lightfrom LEDs 254 from being transmitted in the direction of the driver ofthe vehicle.

Although the structure shown in FIG. 14D shows mirror assembly 510 asincluding the reflector/electrode 120 as illustrated in the embodimentshown in FIG. 14B above, mirror assembly 510 could take on any of theother forms discussed above with respect to the embodiment describedwith respect to FIG. 14A or FIGS. 7A-7G.

Although the present invention has been described as providing a signallight that is used as a turn signal, it will be appreciated by thoseskilled in the art that the signal light could function as any otherform of indicator or signal light. For example, the signal light couldindicate that a door is ajar so as to warn drivers of approachingvehicles that a vehicle occupant may be about to open a door intooncoming traffic, or the light behind the mirror may be an indicatorlight to indicate that the mirror heaters have been turned on, thatanother vehicle is in a blind spot, that the pressure is low, that aturn signal is on, or that freezing/hazardous conditions exist.

While the signal light of the present invention has been described aboveas preferably being made of a plurality of LEDs, the signal light maynevertheless be made of one or more incandescent lamps, or any otherlight source, and an appropriately colored filter without departing fromthe spirit or scope of the present invention.

Yet another embodiment of the present invention is shown in FIGS. 20-22.In this embodiment, an exterior rearview mirror assembly 700 is providedhaving a housing 710 adapted for attachment to the exterior of avehicle. Such mirrors are often mounted to the vehicle door 730 or tothe A-pillar of the vehicle. Within housing 710 is a mirror structure720 and a light source 725 mounted behind mirror structure 720. Mirror720 may be constructed in accordance with any of the above-notedembodiments, such that light emitted from light source 725 may beprojected through mirror 720. Mirror 720 may thus have a reflectorhaving a masked window portion in front of light source 725 or may havea region 726 that is at least partially transmissive provided in frontof light source 725. As yet another alternative, the region 726 in frontof light source 725 may have a construction similar to that shown inFIG. 14 or the entire reflector in mirror 720 may be partiallytransmissive. As shown in FIGS. 21 and 22, light source 725 ispreferably mounted such that it projects light onto a region of thevehicle door 730 on which the vehicle door handle 735 and lock mechanism737 are provided. Lock mechanism 737 may be a keyhole or touch pad ascommonly used to enable the vehicle doors to be locked or unlocked.

Light source 725 may be any type of light source, and is preferably awhite light source. A preferred light source is disclosed incommonly-assigned U.S. Provisional Patent Application No. 60/124,493,entitled “SEMICONDUCTOR RADIATION EMITTER PACKAGE,” filed on Mar. 15,1999, by John K. Roberts, the entire disclosure of which is incorporatedherein by reference.

Light source 725 may be activated so as to project light in response tothe same actions to which the interior vehicle lights are turned on andoff when providing illuminated entry into the vehicle. Thus, forexample, light source 725 may illuminate a portion of door 730 when aperson depresses the lock or unlock key on a key fob associated with thevehicle for remote keyless entry (RKE), when a person attempts to openthe door, or when a person inserts a key into the lock mechanism 737.Alternatively, a motion sensor may be provided to activate light source725. Preferably, light source 725 is disabled so as to be incapable ofprojecting light when the vehicle's ignition has been turned on.

By providing such a light source 725 within exterior rearview mirrorhousing 710, a light source may be mounted on the vehicle forilluminating the area on the exterior of the vehicle where a vehicleoccupant must contact to enter the vehicle. Such a feature isadvantageous when the vehicle is parked in particularly dark locations.

While light source 725 has been described as being mounted to projectlight at door handle 735, it will be appreciated that light source 725could be mounted so as to project light also onto the ground region orother areas of the exterior of the vehicle as well as to the doorhandle. This could be accomplished by providing appropriate opticsbetween light source 725 and mirror structure 720. Additional lightsources could also be mounted so as to project light onto these areas.

The transflective (i.e., partially transmissive, partially reflective)rearview mirror described above allows the display of information to thedriver without removing a portion of the reflective coating. Thisresults in a more aesthetically pleasing appearance and allows themirror to appear as a contiguous reflector when the display is off. Anexample of a display particularly suited to this application is acompass display.

Many mirrors are sold each year which have the added feature ofdisplaying the heading of a vehicle using an alpha-numeric VacuumFluorescent Display (VFD) capable of displaying eight compass directions(N, S, E, W, NW, SW, NE, SE). These types of displays are used in manyother applications in motor vehicles such as radios and clocks. Thesedisplays have a glass cover over the phosphor digit segments. When usedwith a transflective mirror, the majority of the light from the VFD isnot transmitted through the mirror but reflected back to the display. Aportion of this reflected light is then reflected off both the top andbottom surfaces of the cover glass of the VFD and back through themirror. These multi-bounce reflections result is ghost or double imagesin the display which are highly undesired. As discussed above, asolution to this problem is to provide an anti-reflection coating on thecover glass of the VFD, however, such an anti-reflection coating adds tothe cost of the display. Other disadvantages of VFD displays is thatthey are expensive and fragile.

An LED alpha-numeric display is a viable alternative to a vacuumfluorescent display for use in a transflective mirror. As discussedabove, LED displays do not have a specular cover glass and thus do notsuffer from ghost reflection problems. Additionally, the areasurrounding the LEDs can be colored black to further aid in suppressingspurious reflections. LEDs also have the advantage of having extremelyhigh reliability and long life. Segmented alpha-numeric LED displays arecommercially available but are complicated to manufacture and it isdifficult to maintain segment to segment brightness and colorconsistency. Finally, it is also difficult to prevent light from onesegment from bleeding into another segment. LEDs are also only availablein saturated highly monochromatic colors, with the exception of somephosphor-LED combinations, which are currently very expensive. Manyautomotive manufacturers have display color schemes which are more broadspectrum and difficult, if not impossible to match with LEDtechnologies. Most cars manufactured in the United States have a bluedisplay color scheme, which could only be matched with blue LEDs whichare currently very expensive.

An alternative to a segmented LED or VFD display is described below thatovercomes the above problems associated with LEDs and VFDs. While thefollowing description is related to a compass display, the conceptscould readily be extended to a variety of information displays, such asa temperature display and various warning lights. The compass display isused as an example in the preferred embodiment because it bestillustrates the features and advantages of the invention. Also, thefollowing description will concentrate on the use of LEDs as thepreferred light source. However, many other light sources are alsoapplicable, such as incandescent bulbs or new emerging technologies suchas light emitting polymers and organic LEDs. The graphical, rather thanalpha-numerical, nature of this display clearly distinguishes it fromother alpha-numerical displays in a vehicle (such as the clock, etc.).Therefore, it will not look undesirable if this display does not matchthe color scheme of the VFD displays throughout the vehicle, allowingthe use of more efficient and cost effective displays. In fact, thecontrasting colors of the display should contribute to the aesthetics ofthe vehicle interior.

The display in the preferred embodiment consists of multiple LEDs, agraphical applique masking layer, and a transflective mirror. A frontview of the masking layer is shown in FIGS. 23A and 23B. The graphicalapplique shows eight points of a compass (801-808). The applique in FIG.23A includes all eight directions, however, only one of the eightdirections, as shown in FIG. 1 b, will be lit depending on the directionof travel. The region of the mirror containing the other directions willbe reflective and not indicate any content. A center graphic (809) maybe an emblem, such as the globe in FIGS. 23A and 23B, can be added forcosmetic appeal. The globe can be illuminated by an LED of a colorcontrasting the color of the direction indicators.

Various methods of controlling the segments are contemplated. In thesimplest form, only one of the LEDs behind the eight compass directionindicators is illuminated at a given time, depending on the direction oftravel. In another scheme, all eight indicators are lit dimly and theindicator corresponding to the current direction of travel is lit morebrightly than the other eight. In yet another scheme, bicolor LEDs areused and the LED indicator corresponding to the current direction oftravel is set to a different color than the other eight. A finalalternative would be to have only the indicator corresponding to thecurrent direction of travel lit, but gradually fade from one indicatorto another as the car changes directions.

The construction of the display is described with reference to FIGS. 24and 25. FIG. 24 shows the arrangement of LEDs on a circuit board andFIG. 25 shows an exploded view of the display assembly. The LEDs (812)are arranged on a circuit board (811) in a pattern corresponding to thelocations of the indicators and center graphic. LEDs (812) may be of thetype trade named “Pixar” by Hewlett Packard. Due to the loss of light inthe transflective coating, bright LEDs are needed. AlInGaP based LEDsare suitable for this application and are available in greed, red,amber, and various similar colors. Blue and green colors can be achievedby using InGaN LEDs. Although InGaN LEDs are currently expensive, thereare many fewer LEDs needed than would be used in a segmented display. Asan alternative to using packaged LEDs such as the “Pixar” LED, they canbe bonded to the circuit board directly using a technique commonly knownin the industry as Chip-On-Board.

The circuit board (811) is positioned behind the mirror using spacer(813). The spacer (813) serves multiple purposes. First, the spacerpositions the circuit board a distance from the mirror, ¼ inch forexample, such that the light from the LED fully covers the indicator.Second, the spacer prevents cross talk between indicators by preventinglight from one cavity from entering another cavity. To achieve this, thespacer should be made from a white, highly reflective material. At theleast, the spacer must be opaque. Finally, the spacer serves to helpreflect light exiting the LED at high angles back towards the indicator.This improves the efficiency of the system. The spacer may even beconstructed with a parabolic bowl surrounding the LED to mosteffectively direct light forward. A lambertian scattering surface on thespacer will also help diffuse the light and improve the uniformity ofthe indicator illumination. The empty region between the circuit board(811) and the mirror (815) formed by the openings in the spacer (813)may be filled with an epoxy or silicone containing a diffusant. Thiswill help further diffuse the light and help the indicators appear moreuniform.

An applique (814) is provided in a masking layer made of a thin materialwhich has a black matte mask covering all areas but the graphicalindicators. The regions for the graphic are a clear or somewhat whiteand diffuse. The applique may be formed by silk-screening the black maskpattern onto a film of diffuse plastic. Preferably, the side of theapplique facing the LEDs is also screened with a white ink. This willallow light which does not pass through the letters or graphical regionto reflect back onto the LED and spacer where it may then partiallyreflect back forward. Alternatively, the applique can be formed bydirectly silk screening the black mask onto the back surface of mirror(815). The manner by which such an applique may be constructed isdisclosed in U.S. Pat. No. 6,170,956, entitled “REARVIEW MIRRORDISPLAY,” filed on May 13, 1999, by Wayne J. Rumsey et al, the entiredisclosure of which is herein incorporated by reference and furtherdescribed below.

FIG. 26 is a schematic diagram illustrating a vehicle sensor and displaysystem 1000 in accordance with an embodiment of the present invention.The system 1000 includes a passenger sensor 1002, a passenger air bagcontroller 1004, and a passenger air bag status display 1006.Alternatively, the display system could include a manual air bag shutoffswitch in place of, or in addition to, the passenger sensor 1002 and theair bag controller 1004.

The passenger sensor 1002 is used to determine whether a passenger islocated at a particular position in a vehicle. For example, thepassenger sensor 1002 may be used to determine whether a passenger isseated in the right front passenger seat of a car or the like. Thepassenger sensor 1002 may be used to determine the approximate size of apassenger in order to allow deactivation of the passenger's air bag ifthe passenger is less than a particular size. The sensor 1002 may alsobe used to determine whether an infant or child seat is present and todeactivate the air bag if such an infant or child seat is detected.Examples of suitable passenger sensors 1002 include conventionalinfrared sensors, pressure sensors, and the like.

As shown in FIG. 26, the passenger sensor 1002 is connected to thepassenger air bag controller 1004. Based on the signal provided by thepassenger sensor 1002, the controller 1004 switches the passenger airbag on when a suitable size person is positioned in the passenger seat,and switches the air bag off when there is no passenger in the seat.Alternatively, the air bag status display 1006 may be connected directlyto the passenger sensor 1002. Furthermore, the air bag display 1006 maybe connected to a manual air bag shutoff switch (not shown). Thepassenger air bag controller 1004 is connected to the passenger air bagstatus display 1006, as schematically shown in FIG. 26.

In accordance with the present invention, the passenger air bag statusdisplay 1006 is located on a rearview mirror assembly. The display 1006may include any suitable indicia which alerts occupants of the vehiclethat the passenger air bag is either active or inactive. For example,the display 1006 may illuminate the words “PASSENGER AIR BAG OFF” whenthe passenger air bag has been deactivated by the controller 1004 or bya manual switch. Alternatively, the display 1006 may include any othersymbols and/or alphanumeric characters, which adequately conveyinformation concerning the status of the passenger air bag to at leastone occupant of the vehicle.

In accordance with the preferred embodiment of the present invention,the display 1006 is located on the interior rearview mirror assembly ofa vehicle. Vehicle drivers generally look at the interior rearviewmirror very frequently. This frequent use makes the interior rearviewmirror an optimal location for the display of critical safetyinformation, such as air bag status. By displaying safety information onthe interior rearview mirror assembly, the driver or other occupants ofthe vehicle may be alerted to critical information, which couldotherwise go unnoticed.

Examples of suitable displays include LED, vacuum-fluorescent, and LCDdisplays. The display may comprise a filter with words such as “AIRBAG,” an air bag symbol displayed on a surface which would becomevisible, more apparent, or change color when the display is illuminatedor backlighted, or an indicator light or series of lights in a locationrelative to a symbol or text indicative of an air bag, which wouldannounce the activation or deactivation of the air bag system by achange of status or color of the light(s). These indicators and displayscould be located on the assembly supporting and encasing the mirror, ina module supported by but not integral with the mirror assembly, or inthe mirror surface, as more fully described below.

FIG. 27 is a front elevational view of a rearview mirror 1010 inaccordance with an embodiment of the present invention. The rearviewmirror 1010 includes a mirror surface 1011 surrounded by a bezel 1012.In the embodiment shown in FIG. 27, the rearview mirror 1010 is anautomatic interior electrochromic mirror. However, other types ofrearview mirrors including exterior mirrors and prismatic interiormirrors may be provided in accordance with the present invention.

As shown in FIG. 27, a chin 1013 is located at the bottom of the bezel1012. A switch 1014 may be provided inside the chin 1013 in order toturn the automatic electrochromic rearview mirror 1010 on or off. Aconventional light sensor 1015 may be located in the chin 1013 or at anyother suitable location. In addition, an indicator 1016 located in thechin 1013 is used to indicate whether the electrochromic rearview mirror1010 is on or off. Typically, the indicator 1016 includes a light, whichis illuminated when the electrochromic rearview mirror 1010 is on.

In the embodiment of FIG. 27, a passenger air bag status display 1018 islocated in the mirror surface 1011. The display 1018 includes the words“PASSENGER AIR BAG OFF.” However, any other suitable symbolic oralphanumeric indicia which adequately convey the status of the passengerair bag may be used.

In the case of the mirror surface display 1018, any suitable display canbe located in or behind the mirror for viewing through the mirrorassembly. The display 18 may comprise a substantially transparentsection in the mirror. Part or the entire reflective surface may beremoved from a selected area. An indicator light source is positionedbehind the selected area. Removal of any other opaque elements in theaforementioned area are also desirable so that the indicator or displaycan be viewed through the mirror. The removal of the reflective surfacecould create an indicator graphic pattern where desired. For example,the words “PASSENGER AIR BAG OFF” could be etched away from thereflective surface partially or completely to allow transmission oflight from a light source through the graphic pattern to therebyindicate the status of the air bag system.

FIG. 28 is a partially schematic side sectional view showing one type ofrearview mirror display assembly 1020 that may be used in the rearviewmirror 1010 of FIG. 27. The rearview mirror display assembly 1020includes a first glass sheet 1021 which forms a viewing surface facingthe occupant of a vehicle. The viewing surface of the first glass sheet1021 may be smooth or may be provided with a matte texture. A secondglass sheet 1022 is spaced from the first glass sheet 1021. Asubstantially transparent, electrically conductive layer 1023 covers theinterior side of the first glass sheet 1021, while another substantiallytransparent, electrically conductive layer 1024 covers the interior ofthe second glass sheet 1022. An electrochromic composition 1025 fillsthe gap between the glass sheets 1021 and 1022. A reflective layer 1026made of any suitable material, such as silver, is provided on thesurface of the second glass sheet 1022. The display assembly 1020 isthus provided as a part of an electrochromic rearview mirror. Thevarious components of the electrochromic rearview mirror may be arrangedand constructed as disclosed in the previously cited U.S. patentsincorporated herein by reference.

As shown in FIG. 28, a portion of the reflective layer 1026 is removedfrom the glass sheet 1022 in order to provide an opening 1027. Anindicia panel 1028 covers the opening 1027. A light source 1029 isarranged such that upon illumination, light travels through the indiciapanel 1028, opening 1027, and the remaining layers 1021-1025 of theelectrochromic mirror assembly toward the occupant of the vehicle. Theindicia panel 1028 may be unmarked or may comprise any desired indicia,such as alphanumeric symbols or the like. The indicia panel 1028 mayoptionally comprise a color filter. The light source 1029 may compriseany suitable type of illuminator, such as an LED, LCD,vacuum-fluorescent element, incandescent light, or the like.

The display 1018 may thus be part of the silver coating that isetched/removed to form the individual letters or components of thegraphics through which the light would pass to illuminate the letteringor graphics. The display 1018 may further comprise lettering or graphicsprinted or otherwise applied to a cleared area in the silver where thegraphics or lettering would be of a design to show contrast whenilluminated. The graphics or display can be separate from the mirrorelement mounted behind the element, such as a conventional LCD display,a vacuum-fluorescent display, a static mask through which light willpass to display graphics or lettering, or other display types.

A color filter may optionally be included between the display lightsource and the viewer, such as a color filter printed or bonded to themirror surface, or a filter installed on the light source, or at anypoint therebetween. The light source could also be of a bandwidthnarrower than full-spectrum visible light for the purpose of displayinga distinctive color through the display graphics to indicate the statusof the air bag system.

In versions requiring removal of some of the silver surface, a portionrather than all of the silver can be removed in an area and still allowthe display to be seen. One method is to remove a pattern, such as agrid. This allows conduction across a substantial amount of the surfacefacilitating coloring and clearing of the electrochromic substance inthat area proportional to the rest of the element. Another method is toallow breaks in letters and graphics to avoid closed islands in thesurface.

In the embodiment of FIG. 27, the surface of the display 18 is flushwith the surface of the mirror 1010. Alternatively, the surface of thedisplay 18 may be non-planar. For example, the surface of the display 18may comprise a convex arc extending from the surface of the mirror 1010.

In accordance with a preferred embodiment of the present invention, anon-planar display is provided on a rearview mirror assembly. As usedherein, the term “non-planar display” means a display having a contouredexterior viewing surface instead of a flat exterior surface. Preferrednon-planar contoured display surfaces include curved or faceted convexconfigurations.

FIGS. 29-31 illustrate a rearview mirror 1030 having a non-planardisplay in accordance with a preferred embodiment of the presentinvention. The rearview mirror 1030 is an automatic electrochromicmirror including a mirror surface 1031 and a bezel 1032. Although anelectrochromic mirror is shown in FIGS. 29-31, other types of mirrors,such as prismatic rearview mirrors, are within the scope of the presentinvention. A contoured chin 1033 having a curved front face is locatedat the bottom of the bezel 1032. The contoured chin 1033 houses acompass switch 1034, a mirror switch 1035, a light sensor 1036, and anon/off indicator 1037. In this embodiment, a non-planar display 1038 islocated in the chin 1033. As shown most clearly in FIG. 30, the surfaceof the non-planar display 1038 is convex and conforms to the contouredsurface of the chin 1038.

The use of a convex non-planar display 1038 provides substantiallyimproved viewability of the information provided by the display. Thecurved exterior surface of the display 1038 essentially preventsunwanted glare from surrounding light sources and provides improvedviewability to occupants of the vehicle. For example, both the driverand front passenger(s) of the vehicle can readily see the informationprovided by the display 1038 without obstruction. In a preferredembodiment, the non-planar surface of the display 1038 has a mattetexture in order to further reduce unwanted glare.

A display, such as a vacuum-fluorescent, LCD, LED, or the like, may bemounted in the bezel or, preferably, behind a filter in the bezel. Astatic display may simply be illuminated or the illumination colorchanged to display information. This display offers several possibleconfigurations. A preferred display comprises an opening in the bezeland a mask or label with graphics and/or lettering printed onto thesurface to allow light to pass through the lettering or graphics portionof the label. Lettering or graphics molded or embossed into the bezelthrough which light could pass to illuminate the lettering or graphicsmay be used. A translucent bezel or portion of the bezel on which thegraphics could be painted or printed to allow light to pass through onlyselect parts may also be used. Furthermore, printed or molded graphicsor lettering with a corresponding translucent or open section throughwhich light could pass to indicate status may be used. In addition, astatus display of graphics and/or lettering with a corresponding lightwhich illuminates or changes color may be used.

In the embodiment shown in FIGS. 29-31, the rearview mirror 1030includes a compass reading 1039, which indicates the direction in whichthe vehicle is oriented. The compass switch 1034 may be used to turn thecompass reading 1039 on and off. As shown most clearly in FIGS. 30 and31, the rearview mirror 1030 includes a housing 1041 and a conventionalmounting bracket 1042. However, other mounting methods can be used.

FIGS. 32 and 33 illustrate a rearview mirror 1050 in accordance withanother embodiment of the present invention. The electrochromic rearviewmirror 1050 includes a mirror surface 1051 and a surrounding bezel 1052.A chin 1053 having a generally planar front face extends from the bottomof the bezel 1052. The chin 1053 houses a compass switch 1054, a mirrorswitch 1055, a light sensor 1056, and an on/off indicator 1057. A convexnon-planar display 1058 extends from the surface of the chin 1053. Acompass display window 1059 is provided in the mirror surface 1051. Therearview mirror 1050 also includes a housing 1061. The convex surface ofthe non-planar display 1058 shown in FIGS. 32 and 33 substantiallyimproves visibility of the displayed message.

FIGS. 34 and 35 illustrate a rearview mirror 1070 in accordance with afurther embodiment of the present invention. The electrochromic rearviewmirror 1070 includes a mirror surface 1071 surrounded by a bezel 1072. Achin 1073 located at the bottom of the bezel 1072 includes a mirrorswitch 1074, a light sensor 1075, and an on/off mirror indicator 1076. Acrown 1077 having a substantially planar front surface is located at thetop of the bezel 1072. A convex non-planar display 1078 is located inthe crown 1077. The rearview mirror 1070 also includes a housing 1081.

FIGS. 36 and 37 illustrate another rearview mirror 1090 in accordancewith a further embodiment of the present invention. The rearview mirror1090 includes a mirror surface 1091 surrounded by a bezel 1092. A chin1093 located at the bottom of the bezel 1092 houses a mirror switch1094, a light sensor 1095, and an on/off mirror indicator 1096. Theright side of the bezel 1092 includes an extension 1097 having anon-planar display 1098 therein. The rearview mirror 1090 comprises ahousing 1099. In this embodiment, the non-planar display 1098 isoriented such that a passenger seated in the front right seat of avehicle can easily see whether the passenger air bag is on or off.

FIG. 38 is a partially schematic side sectional view illustrating arearview mirror non-planar display assembly 1100 in accordance with anembodiment of the present invention. The non-planar display assembly1100 includes an electrochromic mirror assembly comprising a first glasssheet 1101, a second glass sheet 1102 spaced from the first glass sheet1101, and an electrochromic material 1103 filling the gap between theglass sheets 1101 and 1102. A seal 1104 extends between the glass sheets1101 and 1102 in order to retain the electrochromic material 1103therebetween. Although not shown in FIG. 38, the electrochromic mirrorassembly may include substantially transparent electrically conductivefilms on the interior surfaces of the glass sheets 1101 and 1102, andmay comprise a reflective mirror surface positioned at any suitablelocation, such as the exterior surface of the second glass sheet 1102.Suitable types of electrochromic rearview mirror assemblies aredisclosed in the previously cited U.S. patents which are incorporatedherein by reference.

As shown in FIG. 38, a bezel 1105 contacts the exterior viewing surfaceof the first glass sheet 1101 of the electrochromic mirror assembly. Alamp holder 1106 having a reflective interior surface is formed in thebezel 1105. A light source assembly 1107 is secured in the lamp holder1106. In the embodiment shown in FIG. 38, an LED 1108 is provided aspart of the light source assembly 1107. Alternatively, any othersuitable light source, such as an electroluminescent source,incandescent light, or the like, may be used. An indicia panel 1109covers the lamp holder 1106. The indicia panel 1109 forms the exteriorviewing surface of the display. In accordance with the preferredembodiment of the present invention, the indicia panel 1109 comprises aconvex exterior viewing surface defined by at least one radius ofcurvature, as more fully described below.

The indicia panel 1109 shown in FIG. 38 may be unmarked or may compriseany desired graphics, alphanumeric symbols, or the like. The indiciapanel 1109 may optionally include a color filter.

Preferred non-planar displays of the present invention comprise a convexexterior viewing surface defined by at least one radius of curvature.The radius of curvature may be constant or may vary along the exteriorsurface of the display. For example, in the embodiments shown in FIGS.29-35, the non-planar displays have an exterior curved surface ofsubstantially constant radius defined by an arc swept around asubstantially vertical axis. Such arcs are most readily seen in FIG. 33,element 1058 and in FIG. 35, element 1078. The radius of the arctypically ranges from about 1 cm to about 60 cm, and more preferablyfrom about 1.5 cm to about 15 cm. This geometry results in a displaythat is readily viewed by all occupants of the vehicle while reducingunwanted glare.

In the embodiments of FIGS. 36 and 37, the non-planar display has avarying radius of curvature, which substantially conforms to the curvedbezel surface of the mirror. The non-planar display reduces glare and isreadily viewable to at least the right front passenger of the vehicle.

Conventional planar displays have a high degree of first surfacereflection, which decreases the contrast between the graphics of thedisplay which are intended to be viewed and the reflected light from thesurface. This degrades the ability for a passenger to view the displayedinformation, since the front seat passenger is usually seated in aposition which can create a viewing angle up to 30 degrees or more offof perpendicular to the mirror front surface. A non-planar display, aswell as surface treatment such as a matte finish to decrease thereflection of the surface, increases the contrast of the display,especially when viewed at an angle. The curvature or the display alsoserves to orient the display or a portion of the display toward thepassenger and, therefore, improve the visibility of the display. Alow-glare surface and a convex surface have the added benefit ofreducing glare on the display surface for the driver and other occupantsof the vehicle. Additionally, since the display surface is typically atthe same angle as the mirror surface, glare from the headlamps of afollowing vehicle can also render a glossy, planar display unreadable.

Although the non-planar displays described in the specific embodimentsherein are used to convey information concerning the status of apassenger air bag, other types of symbolic or alphanumeric informationmay be displayed on rearview mirror assemblies in accordance with thepresent invention. For example, the status of other air bags orsupplemental restraint systems in the vehicle may be displayed.Furthermore, information such as door ajar, fasten seat belts, fuelmileage, time, temperature, heading, altitude, and the like may bedisplayed.

A mirror assembly 1115 (also referred to herein as “mirror 1115” herein)(FIGS. 39 and 40) includes a housing 1116 and a bezel 1117 defining acavity 1118, and further includes an electrochromic mirror subassembly1120 1120 (FIG. 50) supported in the cavity 1118 along with a printedcircuit board 1119. The printed circuit board 1119 has a circuit thereonthat is configured to operate the electrochromic mirror subassembly 1120for controlled darkening to reduce glare in the mirror 1115. An indiciapanel 1130 (sometimes called an “applique”) is attached to a rear of themirror subassembly 1120 or bezel 1117 to provide a low cost, highlyattractive lighted display on the mirror 1115. The indicia panel 1130 isconstructed to be exceptionally attractive and effective, as describedbelow. The indicia panel 1130 is constructed with locator-engagingdetails that facilitate its alignment on the mirror subassembly 1120,and further that provide alignment of the mirror subassembly 1120 on thebezel 1117 and in the housing 1116, as also disclosed below.

The illustrated electrochromic mirror subassembly 1120 is commonlyreferred to as a fourth surface reflector, but it is contemplated thatthe present invention will work well with third surface reflectors andwith other mirror constructions. Accordingly, it is contemplated that ascope of the present invention includes all such mirror constructionsand the present description should not be construed as unnecessarilylimiting. The illustrated mirror subassembly 1120 (FIG. 50) includesfront and rear transparent elements 1121 and 1122 (e.g., glass),electrically conductive layers 1123 and 1124 on inner surfaces of thetransparent elements 1121 and 1122, respectively, a layer ofelectrochromic material 1125 located between the conductive layers 1123and 1124, and a reflective layer 1126 on a rear surface of the reartransparent element 1122 (i.e., the “fourth” surface of the mirrorsubassembly 1120). A seal 1125′ extends around an inside perimeter ofthe transparent elements 1121 and 1122 to retain the electrochromicmaterial 1125, when the electrochromic material 1125 is a liquid-phasetype, or gel-phase type, or a hybrid of same. (It is noted that aperimeter edge striping may be applied to transparent elements 1121 and1122 for aesthetics, which results in a similar appearance.) A portionof the reflective layer 1126 is etched away or otherwise removed todefine an elongated opening 1127 (FIG. 43). The indicia panel 1130 isadhered to the reflector layer 1126 in a location 1130′ where it coversthe opening 1127. Light sources 1129 are positioned behind the indiciapanel 1130 to pass light through the indicia panel 1130 and through theopening 1127 of the electrochromic mirror subassembly 1120 toselectively illuminate detailed symbols and information on the indiciapanel 1130 for viewing by a vehicle driver or passengers. A foam lightseal 1134 on the indicia panel 1130 is located between the printedcircuit board 1119 and the indicia panel 1130, and is shaped (see FIG.41) to sealingly engage the printed circuit board 1119 and the indiciapanel 1130 to prevent light leakage around the indicia panel 1130.Specifically, the foam light seal 1134 defines multiple windows1146′-1148′ (FIG. 48) engaging the indicia panel 1130 for containinglight from each of the light sources 1129 (FIG. 42) as each window areais illuminated. The housing 1116 and the bezel 1117 snap together andare shaped to compress together the mirror subassembly 1120, the indiciapanel 1130, the printed circuit board 1119, and the light seal 1134,thus compressing the light seal 1134 to assure good contact by the lightseal 1134.

It is contemplated that the present invention includes many differentindicia panels constructed with light-absorbing material to absorbundesired stray light and reflections, and also constructed with locatortabs and locator features. The illustrated indicia panel 1130 (FIG. 48)includes a body panel 1140 of light-passing translucent or transparentmaterial, such as a mylar sheet, having a rectangular main section 1141and down-angled tabs 1142 at each end. The body panel 1140 includes afront surface treated to minimize the degree to which it will showfingerprints, as known in the art. A locating feature or locator hole1143 is formed in each tab 1142. The holes 1143 are configured to engagelocator protrusions on a fixture (not specifically shown, but see FIG.48) for providing very accurate alignment of the indicia panel 1130 onthe mirror subassembly 1120 when the indicia panel 1130 is adhered to arear surface of the mirror subassembly 1120. The locator holes 1143 arefurther configured to engage a pair of locator protrusions 1170 on thebezel 1117 to very accurately locate the mirror subassembly 1120(including the indicia panel 1130) in the bezel 1117 and mirror housing1116, as described below. When adhesive layer 1055 is eliminated, thelocator holes engage the protrusions 1170 for alignment of the indiciapanel 1130, while other structure on the housing 1116 and bezel 1117align the mirror subassembly 1120.

A light-absorbing layer 1145 of ink, film, paint, or the like is appliedto a back surface of the body panel 1140. The light-absorbing layer 1145accurately forms relatively small and well-defined windows 1146-1148 onthe body panel 1140. One or more layers of semitransparent ortranslucent material 1149-1153 are applied onto the body panel 1140 inthe area of windows 1146-1148 to form the indicia of the present visualdisplay. It is contemplated that the materials 1149-1153 have propertiesallowing them to be accurately applied to form detailed symbols, such asby known printing and symbol forming, film applying processes. Forexample, it is contemplated that the ink could be applied by amulti-coating printing process, or even by an ink-jet printer orcopying/duplicating machine. The illustrated black material 1149includes apertures that form clear lettering. The layer 1150 is appliedbehind the clear lettering and is translucent white, such that the words“PASSENGER AIR BAG” appear when the window 1146 is luminated. Thematerial 1151 is also white and shows through as a symbol of a personwith an air bag inflated in front of the person, but it is contemplatedthat the material 1151 could of course be colored (e.g., orange or red)to highlight and distinguish the symbol. The materials 1152 and 1153form letters for the words “on” and “off,” which are visible only whenthe individual window 1147 or window 1148 are luminated.

In the illustrated indicia panel 1130, an elongated layer 1155 (FIG. 48)of adhesive having a small vertical dimension is applied to a face ofthe body panel 1140 along an upper edge above the windows 1146-1148,with ends of the layer 1155 extending partially downwardly along anupper edge of the down-angled tabs 1142 to form a concavely shapedadhering area on three sides of the indicia forming the visible display.This concave arrangement helps avoid trapping air when adhering theindicia panel 1130 to the mirror subassembly 1120. It also helps reducethermal expansion problems by providing an area in which the body panel1140 can expand or flex. The adhesive layer 1155 is covered with arelease paper 1156 to protect the adhesive during shipping and handlingprior to assembly.

Seal 1134 (FIG. 48) includes a piece of compressible foam 1157 andfurther includes an adhesive-covered face 1158 that adheringly attachesto a back of the light-absorbing layer 1145 on the body panel 1140 ofthe indicia panel 1130. The compressible foam 1157 has windows1146′-1148′ cut into the foam that align with the windows 1146-1148 inthe light-absorbing layer 1145.

The bezel 1117 (FIGS. 42 and 43) is generally oval shaped and configuredto surround and mateably receivingly engage a perimeter of the mirrorsubassembly 1120. A lower horizontal section (FIG. 41) of the bezel 1117includes upper and lower portions 1161 and 1162 that form a window forreceiving finger-actuable switches or buttons 1160 on the mirror 1115.That portion of the bezel 1117 that engages the perimeter of the mirrorsubassembly 1120 includes a rearwardly extending inside section 1163that engages a face of the front transparent element 1121, anaesthetically shaped front or transition area 1164, and a rearwardlyextending outer side section 1165 that extends at least to a positionadjacent an edge of the mirror subassembly 1120. That portion of thebezel 1117 that engages the housing 1116 includes a rearwardly extendingleg or flange 1166 defining an outwardly facing cavity 1167. The housing1116 includes a forwardly extending section 1168 that fits into thecavity 1167 and overlappingly engages the leg 1166. The bezel 1117includes a hook-shaped connector 1169 (FIG. 42) that is constructed tofrictionally snap attach into a recess 1169′ in the housing 1116. Guidefingers 1169″ extend from housing 1116 at locations adjacent thehook-shaped connectors 1169. The fingers 1169″ are shaped to engage aback surface of the flange 1166 in a manner that forces the hook-shapedconnector 1169 into secure engagement with the recess 1169′. It iscontemplated that the hook-shaped connector 1169 and the recess 1169′can be reversed on the housing 1116 and the bezel 1117, or that they canbe replaced with other connection means, such as screws, mechanicalfasteners, adhesive, sonic welding, and the like.

The bezel 1117 (FIG. 43) includes a pair of rearwardly protrudinglocator protrusions 1170 spaced on either side of the indicia panel1130. The protrusions 1170 are shaped to engage the holes 1143 on thetabs 1142 to accurately locate the indicia panel 1130 relative to thebezel 1117. This is very important because the indicia (i.e., thelettering and symbols) on the indicia panel 1130 must be very accuratelyaligned with the bezel 1117 to avoid the appearance of misalignment andpoor quality. Since the indicia panel 1130 is accurately adhered to themirror subassembly 1120, the protrusions 1170 cause the mirrorsubassembly 1120 (including the visible interior of the seal 1134) toalso be accurately aligned with the bezel 1117.

Notably, it is specifically contemplated that adhesive layer 1155 can beeliminated. In such case, the protrusions 1170 accurately locate theindicia panel 1130, while ribs and other structure of the housing 1116and bezel 1117 accurately locate the mirror subassembly 1120.

The printed circuit board 1119 (FIG. 43) includes locator apertures orholes 1173 that also engage the protrusions 1170 to accurately locatethe printed circuit board 1119. The illustrated light sources 1129,which can be any suitable type of illuminator, such as LED, LCD,vacuum-fluorescent elements, incandescent lights, or the like, aremounted to the printed circuit board 1119. Nonetheless, it iscontemplated that the light sources 1129 could be mounted behind theprinted circuit board 1119 and shine through windows in the printedcircuit board 1119. Switches 1160 are also mounted to the printedcircuit board 1119 in a position where they align with lower windows inthe bezel 1117, and where they are easy to operate by a seated driver.

The housing 1116 (FIG. 42) includes sidewalls 1176 having the recesses1169′ and guide fingers 1169″ that receive the hook-shaped connectors1169, and further include a back wall 1177. The back wall 1177 includesmounting structure 1178 for operably adjustably engaging the vehicleball mount 1179 (FIG. 40). Projections 1180 (FIG. 41) extend forwardlyfrom the back wall 1177 into abutting engagement with the printedcircuit board 1119. When assembled, the bezel 1117 snap attaches to thehousing 1116 to compress together the mirror subassembly 1120, theindicia panel 1130, the printed circuit board 1119, and the light seal1134 in a compressed sandwich-like arrangement, with the light seal 1134lightly compressed.

As shown by FIG. 49, the method of assembly includes printing andforming the indicia panel 1130 in a step 1183, and then adhering thefoam light seal 1134 to the indicia panel 1130 in a step 1184. In a step1185, the mirror subassembly 1120 is fixtured by fixtured engagement ofits locator holes 1143, and the indicia panel 1130 is accuratelyattached to the mirror subassembly 1120 (if adhesive is used) byremoving the release paper 1156 and by adhering the adhesive 1155 to arear surface of the rear transparent element 1122 as the indicia panel1130 is accurately held. The indicia panel 1130 is then used toaccurately locate the mirror subassembly 1120 to the bezel 1117 byregistering the holes 1143 on the protrusions 1170 of the bezel 1117 ina step 1186. Alternatively, where adhesive layer 1155 is eliminated,protrusions 1170 engage holes 1143 to locate the indicia panel 1130, butthe mirror subassembly 1120 is located by engagement with the bezel 1117and housing 1116. The printed circuit board 1119 is also accuratelylocated by registering its holes 1173 on the protrusions 1170 in a step1187. The housing 1116 is snap attached to the bezel 1117 in step 1188.This causes the abutting projections 1180 on the housing 1116 to engagethe printed circuit board 1119, compressing the foam light seal 1134between the printed circuit board 1119 and the indicia panel 1130, andcompressing the indicia panel 1130 with light pressure against themirror subassembly 1120. This light pressure helps hold the indiciapanel 1130 against the mirror subassembly 1120, yet permits dimensionalvariation during assembly. This arrangement also allows the expansionand contraction that occurs during thermal cycling of the mirror 1115while in service.

One important benefit of using a light-absorbing indicia panel 1130 isshown in FIG. 50. The light source 1129 emits light 1190, a primaryportion 1191 of which travels through the indicia panel 1130, throughthe opening 1127, and out through various components of the mirrorsubassembly 1120 to a viewing person. Secondary reflections 1192-1196occur at a rear surface of the rear transparent element 1122, and ateach interface between the layers 1122/1124, 1124/1125, 1125/1123, and1123/1121. These secondary reflections 1192-1195 are absorbed by thelight-absorbing layer 1145 on the indicia panel 1130. This arrangementgreatly reduces unwanted stray light. The size of each window 1146-1148and windows 1146′-1148′ (see FIGS. 41-43 and 48), and also the size ofthe opening 1127 (FIG. 50), are chosen to optimize the clarity of theimage projected by primary light portion 1191 without detracting fromthe reflected images of the mirror 1115. In a preferred form, thevertical dimension of the letters and symbols is about 25 percent toabout 75 percent, or more preferably about 50 percent, of the verticaldimension of the opening 1127.

It is noted that mirror subassemblies 1120 having the same size opening1127 can be used in mirrors 1115 having different options. For example,a different indicia panel 1130 can be used along with different printedcircuits boards 1119, while still using the same bezel 1117, housing1116, and mirror subassembly 1120. This greatly facilitatesmanufacturing high volumes of mirror subassemblies 1120 while stillallowing for a maximum of options. Further, the same housing 1116 andmirror subassembly 1120 can be used, while using a different bezel 1117.This is an important advantage since the mirror subassembly 1120 is oneof the more expensive components of the mirror 1115. It is important tohave the mirror subassembly 1120 be at a higher volume to optimizeautomation of the manufacturing process and to minimize costs.

It is specifically contemplated that aspects of the present inventioncan be utilized advantageously in different mirror constructions. Onesuch mirror is illustrated in FIG. 51, and includes a front-mountedindicia panel 1130A adheringly attached to a front surface of the fronttransparent element 1121A. In mirror 1115A, components and features thatare identical or similar to the features and components of mirror 1115are identified by the same number, but with the addition of the letterA.

In mirror 1115A, the indicia panel 1130A is adhered to the front surfaceusing adhesive 1155A, and the light-absorbing layer 1145A is locatedadjacent the adhesive 1155A. Notably, it is contemplated that theadhesive 1145A could be omitted where the indicia panel 1130A isadequately supported by portions of the bezel 1117A. It is alsocontemplated that the light-absorbing layer 1145A could be positioned onthe other side of the indicia panel 1130A or even on any of the front orrear surfaces of the transparent elements 1121A and 1122A. The indiciapanel 1130A provides many of the advantages noted above, includingfixturing advantages, good appearance, low cost, and a flexible partthat can be used in mirrors having different options.

While the invention has been described in detail herein in accordancewith certain preferred embodiments thereof, many modifications andchanges therein may be effected by those skilled in the art withoutdeparting from the spirit of the invention. Accordingly, it is ourintent to be limited only by the scope of the appending claims and notby way of the details and instrumentalities describing the embodimentsshown herein.

1. A rearview mirror assembly for use in a vehicle, the assemblycomprising: a first substantially transparent substrate and a secondsubstantially transparent substrate secured behind the first substrate,said second substrate including a layer of reflective material beingproximate a surface of said second substrate that is closest to saidfirst substantially transparent substrate, and a first layer ofsubstantially transparent conductive material positioned between thelayer of reflective material and the first substantially transparentsubstrate, wherein the assembly comprises a transmittance of at leastabout 5 percent in at least portions of the visible spectrum, and a C*value of less than about 20 measured in reflected ambient light.
 2. Arearview mirror assembly according to claim 1 further comprising asecond layer of substantially transparent conductive material positionedbetween said layer of reflective material and said second substrate. 3.A rearview mirror assembly according to claim 2, wherein the secondlayer of substantially transparent conductive material comprises zinc.4. A rearview mirror assembly according to claim 1, wherein said firstlayer of substantially transparent conductive material comprises zinc.5. A rear view mirror assembly according to claim 1, wherein said layerof reflective material is made of a silver alloy including a combinationof silver and an element selected from a group consisting of gold,platinum, rhodium, and palladium.
 6. A rearview mirror assemblyaccording to claim 1, wherein the electrochromic mirror has areflectance of at least 35 percent.
 7. A method for operating a rearviewmirror assembly, the method comprising: transmitting light from a lightsource within the assembly through an optical system to a field of viewoutside the assembly, wherein the optical system includes a firstsubstrate having first and second surfaces, the first surfacecorresponding to an outside portion of the assembly, and a secondsubstrate having a third surface, the second substrate secured to thefirst substrate, the third surface facing the second surface; andpartially transmitting light incident on the third surface in such amanner as to provide for transmittance, by the optical system, of thelight from the light source, of at least 5 percent in at least portionsof the visible spectrum, wherein the assembly comprises at least one ofa b* value of less than about 15 and a C* value of less than about 20measured in reflected ambient light.
 8. A method according to claim 7,further comprising: partially reflecting light incident on the thirdsurface in such a manner as to provide for reflectance, by the opticalsystem, of ambient light incident onto the assembly from the field ofview outside the assembly, of at least 35 percent.
 9. A method accordingto claim 7, wherein said assembly has a reflectance of at least about 65percent.
 10. A method according to claim 7, wherein the transmittance oflight from the light source through the optical system is at least 10percent.
 11. A method according to claim 7, wherein the light source isa display.
 12. A method for operating a rearview mirror assembly, themethod comprising: transmitting light from a light source within theassembly through an optical system to a field of view outside theassembly, wherein the optical system includes a first substrate havingfirst and second surfaces, the first surface corresponding to an outsideportion of the assembly, and a second substrate having a third surface,the second substrate secured to the first substrate, the third surfacefacing the second surface; and partially transmitting light incident onthe third surface in such a manner as to provide for transmittance, bythe optical system, of the light from the light source, of at least 5percent in at least portions of the visible spectrum, wherein theassembly comprises a C* value of less than about 20 measured inreflected ambient light and wherein reflecting light incident on thethird surface includes reflecting light with an electrode overlying thethird surface, said electrode comprising: a first layer of a firstmaterial having a relatively high refractive index; a second layer of asecond material having a relatively low refractive index, the secondlayer being disposed on the first layer; and a third layer of a thirdmaterial having a relatively high refractive index, the third layerbeing disposed on the second layer.
 13. A method according to claim 12,wherein the second material is a silver alloy including a combination ofsilver and an element selected from the group consisting of gold,platinum, rhodium, and palladium.
 14. A method according to claim 12,wherein the second material is a silver alloy including about 94 percentsilver and about 6 percent gold.
 15. A method according to claim 12,wherein the electrode further comprises a forth layer of a transparentconductive material, the forth layer being deposited on the third layer.